An idea how to solve some of the problems. diverges the same must hold for the original series. T 1 p T 1 p + 1 p 1 = 1. dt = lim
|
|
- Quentin Griffin
- 5 years ago
- Views:
Transcription
1 An idea how to solve some of the problems (a) Does not converge: By multiplying across we get Hence 2k 2k 2 /2 k 2k2 k 2 /2 k 2 /2 2k 2k 2 /2 k. As the series diverges the same must hold for the original series. k (b) Converges: We have (k )/(k2 k ) 2 k and the series 2 k converges. (c) Divergent: In this case /(2k ) > /(2k) (multiply in cross) and the series /k diverges. (d) Divergent: Assume first that p > and take f(x) = x p. Then f is monotonically decreasing to zero. Furthermore T f(t)dt t p dt T T p T p + p = p <. The claim follows then from Theorem Let now p =. We have T x dx = log T as T. It follows that /x dx does not exists and hence k does not converge according to Theorem If p then /k p /k and hence k p diverges Suppose x k for all k N, and suppose that lim k k x k = L exists. (a) If L > then x k diverges: Let < r < L. Then there exists N N such that for all n N we have r k x k. Hence x k r k. The claim follows now because k=n rk does not exists. (b) If L < then x k converges: Let L < r <. Then there exists N N such that k x k r for all n N. This implies that x k r k and hence x k = x x N + x x N + k=n x k r k <. k=n
2 Hence the series converges. (c) If L = there is no information: Let x k = for all k. Then k x k = and the series x k diverges. On the other hand, if x k = k 2 then lim k k x k = as we will see in a moment and this time the series x k converges. Let n N and consider the sequence x k = k k n. Taking the log we see that (using L Hospital) Hence lim log x n log k k k k k lim x k = e =. k n k k =. 5.2-: Test for convergence: (a) k!/kk : Convergent because with x k = k!/k k we have x k+ x k = (k + )!kk k!(k + ) k+ = ( + /k) k /e <. (b) k/e k2 : Convergent because (k + )e k2 ke (k+)2 = ( + /k)e 2k as k. (c) k=2 /(log k)k : Convergent. Use the root test (fill in the details) We have 3 k 4 = k 3 k 4 k = 2 3 = If the sequence {c k } is summable then it follows that c k is bounded, i.e., there exists a C > such that c k C for all k (use that lim c k = ). Hence c k x k C x k <
3 for x <. If x = then c k x k = c k is summable by our assumption on c k We do (a) Let ɛ > be given. Let N > 2/ɛ. Then, if n > m N there exists µ (/n, /m) such that ( f(/n) f(/m) = f (µ) n ) m As f (µ) < it follows that f(/n) f(/m) < n m < 2 N < ɛ. It follows that {f(/n)} is a Cauchy sequence and hence exists. lim f(/n) = L n (b) Let now {x k } be an arbitrary sequence x k. Then, by the same argument as above it follows that {f(x k )} is a Cauchy sequence and hence lim f(x k ) = L exists. Define a new sequence y 2k = /k and y 2k+ = x k. Then y k and the above argument show that lim k f(y k ) exists. Add the details to show that this implies that L = L (use subsequence) It was shown that all the limits exists, so we will not do it here (on an exam you would have to do the details). Let v, w V and c R. Then T n (cv + w) = ct n (v) + T n (w) because T n is linear. As all the limits exists we have: which shows that T is linear. T (cv + w) (T n (cv + w)) n (ct n (v) + T n (w)) n = c lim T n (v) + lim T n (w) n n = ct (v) + T (w) First we have to show that is a norm on l. Let x = {x k }, y = {y k } l and c R. Note first that cx k + y k cx k + y k = c x k + y k.
4 Hence cx + y = sup cx k + y k k ( cx k + y k ) sup k c sup k = c x + y x k + sup y k k Furthermore x = if and only if all x k = which happen if and only if x =. Next we have to show that l is complete. Let {x n } be a Cauchy sequence in l. Let ɛ > be given. Then there exists N N such that for all n, m N we have x n x m = sup x n k x m k < ɛ/2. k It follows that the sequence {x n k } n is a Cauchy sequence in R and hence there exists a x k R such that x n k x k. Let x = {x k } we have to show that x n x and that x l. Let N be as above. Then x n k xm k < ɛ/2. Letting m this implies that Thus and x n k x k ɛ/2 < ɛ. ( n N) x n x < ɛ x = x x N + x N x x N + x N < ɛ + x N <. This proves both statements : Recall that the sequence x n l is defined by x n k = (n + )/(n2k ). a) Show that x n l : We have x n = n + n 2 k 2 2 k < because n + n + /n 2.
5 b) By the above we have that lim n infty xn k = 2 k = x k exists and the sequence x = {x k } is in l because 2 k <. c) We have x n k x k =. Furthermore n2 k 2 k =. Hence x n x = x n k x k = n. Let ɛ >. Let N N be such that N > /ɛ. Then, if n N we have x n x = n N < ɛ In this problem we define x n by x n k = if k n and xn k = k 2 if k > n. (a) We have Hence x n l. x n = x n k = n + k=n+ k 2 <. () (b) Let k N, then for all n k we have x n k =. Hence x k n x n k = for all k. In particular x = {x k } l. (c) The sequence {x n } can not be a Cauchy sequence because otherwise lim x n = x l would exists If α < show that xk conveges uniformly on [, α]. Solution: We have M k = sup x [,α] x k = α k and hence the series M k converges. The claim follows by the Weierstrass M-test : If f k converges uniformly on D, prove that f n as n. Is the converse true? Solution: As f k converges uniformly it follows that the sequence of partial sums s n = n f k is a Cauchy sequence in the supremum norm. Let ɛ >. Then there exists a N N such that n, m N s n s m < ɛ. In particular for n > N: f n = s n s n < ɛ.
6 The converse is not true. For that let f k (x) = k on [, ]. Then f k = /k, but f k(x) does not even converge at x = : (a) The sequence e kx converges uniformly on [, ). For that note that on this interval we have e kx e k = (/e) k and the series (/e)k converges. The claim follows then by the Weierstrass M-test. (b) sin(kx) converges uniformly on R because k 3 sin(kx) k 3 k 3 and the series /k3 converges. The claim follows then by the Weierstrass M-test. (c) The series sink (x) converges uniformly on [, π/4] because on this interval sin k (x) (/ 2) k and the series (/ 2) k converges. (d) No, the series tank x does not even converge at x = π/ : (a) We have to show that ( ) k 2k + x2k+ = x ( ) k 2k + x2k converges uniformly on [, ]. We note that for all x [, ] the series ( ) k 2k+ x2k is alternating and x k = x2k monotonically. Hence 2k+ k x k exists and by Theorem 5..2 we we have with s n (x) = n Hence which proves the claim. ( ) k 2k+ x2k and s(x) = ( ) k 2k+ x2k : xs n (x) xs(x) = x s n (x) s(x) x n+ = x n ( ) k 2k + x2k+ s(x) x 2n 2n + 2 2(n + ). 2(n + ) (b) Define g(x) = ( ) k 2k+ x2k then it follows by (a) and Theorem 5.5., part a, it follows that g(x) is continuous on [, ]. As g(x) = tan (x) for x (, ) and tan x is continuous, it follows that g(±) = tan (±).
7 (c) We know that tan () = π 4. Hence π = 4 tan () = 4 ( ) k 2k : We have tk = t Taking t = /2 we get if t <. Hence, by Theorem 5.6. and Theorem 5.5.: t k+ k + = t k k = t du = log( u). u = log(/2) = log 2. k2k 5.6-5: Find the interval of convergence of the series c k x k. We use the ratio test: In case lim c k+ k c k = L exists, then R = L. (In case L = this reads R = and L = reads R =.) (a) c k = /(k!). Then c k+ = c k k +. Hence the power series converges for all x R. (b) a = and c k = ( ) k+ /(k + ). Then lim c k+ k c k = and hence R =. If x =, then we have a alternating series so the power series converges at x =. If x = 2 then we are looking at the series ( ) 2k+ k +
8 which does not converge. So the power series converges on ( 2, ]. (c) c k = k!/k k so ( ) k (k + )!kk c k+ /c k = k!(k + ) = /e. k+ + /k What about the endpoint? (d) c k = /k k. Then c k+ /c k = k k (k + ) = ( ) k k k+ k + (k + ) k +. Hence the power series converges for all x R, i.e, R = : The function e x is analytic at and so is tan (x). It follows by Theorem that e x tan x is analytic at. There are two ways to find the coefficient of x 4. First, just differentiate the function four times and use that c k = f (k) ()/k!. The other way is to use that if f(x) = a kx k and g(x) = b kx k for x R, then ( k ) fg(x) = a k b j x j+k = a j b k j x k. Hence the coefficient of x k is j= k a j b k j. It follows then from formula (5.2) p. 4 that the coefficient of x 4 is j= j= j= 4 ( ) 4 j j! 2(4 j) + = = simplify : We have tan (x) = ( ) k 2k + x2k+ = f (k) () k! Note, that the coefficients for the even powers of x are all zero. Hence f (even) () =. In particular f () () =. We have = 2 5 +, so k = 5, and hence f () () =! =!. x k.
9 5.7-4: (a) The function f(x) = x can not be analytic at zero, because it is not differentiable at zero (recall: analytic functions are smooth!). (b) The function can not be analytic at zero because we have { k!x, x > f (k ) (x) =, x and this function is not differentiable at zero : (a) True, the function is given by f(x) = x 4 on the interval (, ). (b) True, we have f(x) = on the interval (, ). (c) No (see problem with k = Let f(x) = { e /x 2, x, x =. Note that f is -times differentiable at all points x as that holds for the exponential function and the function x /x 2. (a) To see if f () we need to see if the limit f(h) f() lim h h e /h2 h h exists. Note that this limit is of the form so we can use L Hospital. We set u = /h and consider the limit u : e /h2 lim h h u = u e u2 2ue u2 u Hence, f () exists and is equal to zero, f () =. Before we do the next parts let us note the following: Let k N, then e /h2 u k lim h h k u e u2
10 ku k u 2ue u2 u k(k )u k 2 2e u2 + 4u 2 e u2 = q(u)e u2 u k! where q(u) = 2 k u k +... is a polynomial of degree k. (b) We have { f 2e /x 2 /x (x) = 3, x, x =. Hence, by the above argument f (h) f () h = 2e /h2 h 4 h. Hence the derivative at zero exists and f () =. (c) Use induction to show that there exists an n N and constants c j, j =,..., n such that f (k) (x) = { n j= c j e /x 2, x x j, x = Hence, the above argument shows, that f (k+) (x) exists for all x R and f (k+) () = : We have Hence sin(x) x is analytic and (Fill in the details.) sin(x) = sin(x) = ( ) k (2k + )! x2k+. ( ) k (2k + )! x2k. 5.8-: The function f(x) = /x is unbounded around, whereas every polynomial is bounded. Hence, assume that p(x) is a polynomial. Then f(x) p(x) =. x (,)
11 5.8-2: The function f(x) = e x is unbounded on R. Even more holds. Let p(x) = n j= a jx j be a polynomial with a n. Then for x big, we have e x p(x) = x n e x x a n n a n /x... a /x n as x : (a) Assume that f C([, ]) and that f(x)xk dx = for all k =,,.... Assume that f, Then Let p(x) be a polynomial. Then and f(x) 2 dx = A >. f(x)p(x) dx = f p 2 (f(x) p(x)) 2 dx = f(x) 2 dx 2 f(x)p(x) dx + p(x) 2 dx A >. Let < ɛ < A. Then, by Weierstrass Approximation Theorem, there exists a polynomial p such that f p < ɛ < A a contradiction. (b) Define T k (f) = f(x)xk dx, k =,,.... Then T k (af + g) = at k (f) + T k (g) because the Riemann integral is linear. Furthermore T k (f) = f(x)x k dx f(x) x k dx f x k dx = f k +.
12 Hence T k is bounded. (c) Assume that f, g C([, ]) and that T k (g) = T k (f). Then T k (g f) = for all k and hence by (a) g f = or g = f : Let k(x) = 2 χ [,](x) where χ [,] denotes the indicator function of the interval [, ]. Then k n (x) = nk(nx) = n 2 χ [ /n,/n] (fill in the detail) and k n (x) dx = n 2 /n /n dx =. If δ >, then there exists an n N such that n < δ and hence k n(x) = for δ x.
d(x n, x) d(x n, x nk ) + d(x nk, x) where we chose any fixed k > N
Problem 1. Let f : A R R have the property that for every x A, there exists ɛ > 0 such that f(t) > ɛ if t (x ɛ, x + ɛ) A. If the set A is compact, prove there exists c > 0 such that f(x) > c for all x
More informationMath 140A - Fall Final Exam
Math 140A - Fall 2014 - Final Exam Problem 1. Let {a n } n 1 be an increasing sequence of real numbers. (i) If {a n } has a bounded subsequence, show that {a n } is itself bounded. (ii) If {a n } has a
More informationPrinciple of Mathematical Induction
Advanced Calculus I. Math 451, Fall 2016, Prof. Vershynin Principle of Mathematical Induction 1. Prove that 1 + 2 + + n = 1 n(n + 1) for all n N. 2 2. Prove that 1 2 + 2 2 + + n 2 = 1 n(n + 1)(2n + 1)
More informationMath 328 Course Notes
Math 328 Course Notes Ian Robertson March 3, 2006 3 Properties of C[0, 1]: Sup-norm and Completeness In this chapter we are going to examine the vector space of all continuous functions defined on the
More informationSolutions Final Exam May. 14, 2014
Solutions Final Exam May. 14, 2014 1. (a) (10 points) State the formal definition of a Cauchy sequence of real numbers. A sequence, {a n } n N, of real numbers, is Cauchy if and only if for every ɛ > 0,
More informationMeasure and Integration: Solutions of CW2
Measure and Integration: s of CW2 Fall 206 [G. Holzegel] December 9, 206 Problem of Sheet 5 a) Left (f n ) and (g n ) be sequences of integrable functions with f n (x) f (x) and g n (x) g (x) for almost
More informationMath 117: Infinite Sequences
Math 7: Infinite Sequences John Douglas Moore November, 008 The three main theorems in the theory of infinite sequences are the Monotone Convergence Theorem, the Cauchy Sequence Theorem and the Subsequence
More informationConvergence of sequences and series
Convergence of sequences and series A sequence f is a map from N the positive integers to a set. We often write the map outputs as f n rather than f(n). Often we just list the outputs in order and leave
More informationAdvanced Calculus Math 127B, Winter 2005 Solutions: Final. nx2 1 + n 2 x, g n(x) = n2 x
. Define f n, g n : [, ] R by f n (x) = Advanced Calculus Math 27B, Winter 25 Solutions: Final nx2 + n 2 x, g n(x) = n2 x 2 + n 2 x. 2 Show that the sequences (f n ), (g n ) converge pointwise on [, ],
More informationSummer Jump-Start Program for Analysis, 2012 Song-Ying Li. 1 Lecture 7: Equicontinuity and Series of functions
Summer Jump-Start Program for Analysis, 0 Song-Ying Li Lecture 7: Equicontinuity and Series of functions. Equicontinuity Definition. Let (X, d) be a metric space, K X and K is a compact subset of X. C(K)
More informationReal Analysis Problems
Real Analysis Problems Cristian E. Gutiérrez September 14, 29 1 1 CONTINUITY 1 Continuity Problem 1.1 Let r n be the sequence of rational numbers and Prove that f(x) = 1. f is continuous on the irrationals.
More informationCALCULUS JIA-MING (FRANK) LIOU
CALCULUS JIA-MING (FRANK) LIOU Abstract. Contents. Power Series.. Polynomials and Formal Power Series.2. Radius of Convergence 2.3. Derivative and Antiderivative of Power Series 4.4. Power Series Expansion
More informationReal Analysis Math 131AH Rudin, Chapter #1. Dominique Abdi
Real Analysis Math 3AH Rudin, Chapter # Dominique Abdi.. If r is rational (r 0) and x is irrational, prove that r + x and rx are irrational. Solution. Assume the contrary, that r+x and rx are rational.
More informationconverges as well if x < 1. 1 x n x n 1 1 = 2 a nx n
Solve the following 6 problems. 1. Prove that if series n=1 a nx n converges for all x such that x < 1, then the series n=1 a n xn 1 x converges as well if x < 1. n For x < 1, x n 0 as n, so there exists
More informationProblem 3. Give an example of a sequence of continuous functions on a compact domain converging pointwise but not uniformly to a continuous function
Problem 3. Give an example of a sequence of continuous functions on a compact domain converging pointwise but not uniformly to a continuous function Solution. If we does not need the pointwise limit of
More information1 Homework. Recommended Reading:
Analysis MT43C Notes/Problems/Homework Recommended Reading: R. G. Bartle, D. R. Sherbert Introduction to real analysis, principal reference M. Spivak Calculus W. Rudin Principles of mathematical analysis
More informationSection Taylor and Maclaurin Series
Section.0 Taylor and Maclaurin Series Ruipeng Shen Feb 5 Taylor and Maclaurin Series Main Goal: How to find a power series representation for a smooth function us assume that a smooth function has a power
More informationMATH 202B - Problem Set 5
MATH 202B - Problem Set 5 Walid Krichene (23265217) March 6, 2013 (5.1) Show that there exists a continuous function F : [0, 1] R which is monotonic on no interval of positive length. proof We know there
More informationThe reference [Ho17] refers to the course lecture notes by Ilkka Holopainen.
Department of Mathematics and Statistics Real Analysis I, Fall 207 Solutions to Exercise 6 (6 pages) riikka.schroderus at helsinki.fi Note. The course can be passed by an exam. The first possible exam
More informationSolutions Final Exam May. 14, 2014
Solutions Final Exam May. 14, 2014 1. Determine whether the following statements are true or false. Justify your answer (i.e., prove the claim, derive a contradiction or give a counter-example). (a) (10
More information1. For each statement, either state that it is True or else Give a Counterexample: (a) If a < b and c < d then a c < b d.
Name: Instructions. Show all work in the space provided. Indicate clearly if you continue on the back side, and write your name at the top of the scratch sheet if you will turn it in for grading. No books
More informationSolutions: Problem Set 4 Math 201B, Winter 2007
Solutions: Problem Set 4 Math 2B, Winter 27 Problem. (a Define f : by { x /2 if < x
More informationSequences. Chapter 3. n + 1 3n + 2 sin n n. 3. lim (ln(n + 1) ln n) 1. lim. 2. lim. 4. lim (1 + n)1/n. Answers: 1. 1/3; 2. 0; 3. 0; 4. 1.
Chapter 3 Sequences Both the main elements of calculus (differentiation and integration) require the notion of a limit. Sequences will play a central role when we work with limits. Definition 3.. A Sequence
More informationContinuity. Chapter 4
Chapter 4 Continuity Throughout this chapter D is a nonempty subset of the real numbers. We recall the definition of a function. Definition 4.1. A function from D into R, denoted f : D R, is a subset of
More informationContinuous Functions on Metric Spaces
Continuous Functions on Metric Spaces Math 201A, Fall 2016 1 Continuous functions Definition 1. Let (X, d X ) and (Y, d Y ) be metric spaces. A function f : X Y is continuous at a X if for every ɛ > 0
More informationProblem Set 5: Solutions Math 201A: Fall 2016
Problem Set 5: s Math 21A: Fall 216 Problem 1. Define f : [1, ) [1, ) by f(x) = x + 1/x. Show that f(x) f(y) < x y for all x, y [1, ) with x y, but f has no fixed point. Why doesn t this example contradict
More informationMath 651 Introduction to Numerical Analysis I Fall SOLUTIONS: Homework Set 1
ath 651 Introduction to Numerical Analysis I Fall 2010 SOLUTIONS: Homework Set 1 1. Consider the polynomial f(x) = x 2 x 2. (a) Find P 1 (x), P 2 (x) and P 3 (x) for f(x) about x 0 = 0. What is the relation
More informationMATH 1372, SECTION 33, MIDTERM 3 REVIEW ANSWERS
MATH 1372, SECTION 33, MIDTERM 3 REVIEW ANSWERS 1. We have one theorem whose conclusion says an alternating series converges. We have another theorem whose conclusion says an alternating series diverges.
More informationAnalysis Qualifying Exam
Analysis Qualifying Exam Spring 2017 Problem 1: Let f be differentiable on R. Suppose that there exists M > 0 such that f(k) M for each integer k, and f (x) M for all x R. Show that f is bounded, i.e.,
More informationStudy # 1 11, 15, 19
Goals: 1. Recognize Taylor Series. 2. Recognize the Maclaurin Series. 3. Derive Taylor series and Maclaurin series representations for known functions. Study 11.10 # 1 11, 15, 19 f (n) (c)(x c) n f(c)+
More informationFunctions. Chapter Continuous Functions
Chapter 3 Functions 3.1 Continuous Functions A function f is determined by the domain of f: dom(f) R, the set on which f is defined, and the rule specifying the value f(x) of f at each x dom(f). If f is
More informationMath 118B Solutions. Charles Martin. March 6, d i (x i, y i ) + d i (y i, z i ) = d(x, y) + d(y, z). i=1
Math 8B Solutions Charles Martin March 6, Homework Problems. Let (X i, d i ), i n, be finitely many metric spaces. Construct a metric on the product space X = X X n. Proof. Denote points in X as x = (x,
More informationMAT 570 REAL ANALYSIS LECTURE NOTES. Contents. 1. Sets Functions Countability Axiom of choice Equivalence relations 9
MAT 570 REAL ANALYSIS LECTURE NOTES PROFESSOR: JOHN QUIGG SEMESTER: FALL 204 Contents. Sets 2 2. Functions 5 3. Countability 7 4. Axiom of choice 8 5. Equivalence relations 9 6. Real numbers 9 7. Extended
More information1 + lim. n n+1. f(x) = x + 1, x 1. and we check that f is increasing, instead. Using the quotient rule, we easily find that. 1 (x + 1) 1 x (x + 1) 2 =
Chapter 5 Sequences and series 5. Sequences Definition 5. (Sequence). A sequence is a function which is defined on the set N of natural numbers. Since such a function is uniquely determined by its values
More informationAssignment-10. (Due 11/21) Solution: Any continuous function on a compact set is uniformly continuous.
Assignment-1 (Due 11/21) 1. Consider the sequence of functions f n (x) = x n on [, 1]. (a) Show that each function f n is uniformly continuous on [, 1]. Solution: Any continuous function on a compact set
More informationh(x) lim H(x) = lim Since h is nondecreasing then h(x) 0 for all x, and if h is discontinuous at a point x then H(x) > 0. Denote
Real Variables, Fall 4 Problem set 4 Solution suggestions Exercise. Let f be of bounded variation on [a, b]. Show that for each c (a, b), lim x c f(x) and lim x c f(x) exist. Prove that a monotone function
More informationContinuity. Chapter 4
Chapter 4 Continuity Throughout this chapter D is a nonempty subset of the real numbers. We recall the definition of a function. Definition 4.1. A function from D into R, denoted f : D R, is a subset of
More information1. Let A R be a nonempty set that is bounded from above, and let a be the least upper bound of A. Show that there exists a sequence {a n } n N
Applied Analysis prelim July 15, 216, with solutions Solve 4 of the problems 1-5 and 2 of the problems 6-8. We will only grade the first 4 problems attempted from1-5 and the first 2 attempted from problems
More informationCopyright 2010 Pearson Education, Inc. Publishing as Prentice Hall.
.1 Limits of Sequences. CHAPTER.1.0. a) True. If converges, then there is an M > 0 such that M. Choose by Archimedes an N N such that N > M/ε. Then n N implies /n M/n M/N < ε. b) False. = n does not converge,
More informationConstructing Approximations to Functions
Constructing Approximations to Functions Given a function, f, if is often useful to it is often useful to approximate it by nicer functions. For example give a continuous function, f, it can be useful
More informationReal Analysis Notes. Thomas Goller
Real Analysis Notes Thomas Goller September 4, 2011 Contents 1 Abstract Measure Spaces 2 1.1 Basic Definitions........................... 2 1.2 Measurable Functions........................ 2 1.3 Integration..............................
More informationMATH NEW HOMEWORK AND SOLUTIONS TO PREVIOUS HOMEWORKS AND EXAMS
MATH. 4433. NEW HOMEWORK AND SOLUTIONS TO PREVIOUS HOMEWORKS AND EXAMS TOMASZ PRZEBINDA. Final project, due 0:00 am, /0/208 via e-mail.. State the Fundamental Theorem of Algebra. Recall that a subset K
More informationExercises from other sources REAL NUMBERS 2,...,
Exercises from other sources REAL NUMBERS 1. Find the supremum and infimum of the following sets: a) {1, b) c) 12, 13, 14, }, { 1 3, 4 9, 13 27, 40 } 81,, { 2, 2 + 2, 2 + 2 + } 2,..., d) {n N : n 2 < 10},
More informationMcGill University Math 354: Honors Analysis 3
Practice problems McGill University Math 354: Honors Analysis 3 not for credit Problem 1. Determine whether the family of F = {f n } functions f n (x) = x n is uniformly equicontinuous. 1st Solution: The
More informationSome analysis problems 1. x x 2 +yn2, y > 0. g(y) := lim
Some analysis problems. Let f be a continuous function on R and let for n =,2,..., F n (x) = x (x t) n f(t)dt. Prove that F n is n times differentiable, and prove a simple formula for its n-th derivative.
More informationSec 4.1 Limits, Informally. When we calculated f (x), we first started with the difference quotient. f(x + h) f(x) h
1 Sec 4.1 Limits, Informally When we calculated f (x), we first started with the difference quotient f(x + h) f(x) h and made h small. In other words, f (x) is the number f(x+h) f(x) approaches as h gets
More information10.1 Sequences. Example: A sequence is a function f(n) whose domain is a subset of the integers. Notation: *Note: n = 0 vs. n = 1.
10.1 Sequences Example: A sequence is a function f(n) whose domain is a subset of the integers. Notation: *Note: n = 0 vs. n = 1 Examples: EX1: Find a formula for the general term a n of the sequence,
More informationChapter 8: Taylor s theorem and L Hospital s rule
Chapter 8: Taylor s theorem and L Hospital s rule Theorem: [Inverse Mapping Theorem] Suppose that a < b and f : [a, b] R. Given that f (x) > 0 for all x (a, b) then f 1 is differentiable on (f(a), f(b))
More informationIowa State University. Instructor: Alex Roitershtein Summer Homework #5. Solutions
Math 50 Iowa State University Introduction to Real Analysis Department of Mathematics Instructor: Alex Roitershtein Summer 205 Homework #5 Solutions. Let α and c be real numbers, c > 0, and f is defined
More information201B, Winter 11, Professor John Hunter Homework 9 Solutions
2B, Winter, Professor John Hunter Homework 9 Solutions. If A : H H is a bounded, self-adjoint linear operator, show that A n = A n for every n N. (You can use the results proved in class.) Proof. Let A
More informationf (x) = k=0 f (0) = k=0 k=0 a k k(0) k 1 = a 1 a 1 = f (0). a k k(k 1)x k 2, k=2 a k k(k 1)(0) k 2 = 2a 2 a 2 = f (0) 2 a k k(k 1)(k 2)x k 3, k=3
1 M 13-Lecture Contents: 1) Taylor Polynomials 2) Taylor Series Centered at x a 3) Applications of Taylor Polynomials Taylor Series The previous section served as motivation and gave some useful expansion.
More informationSolutions to Assignment-11
Solutions to Assignment-. (a) For any sequence { } of positive numbers, show that lim inf + lim inf an lim sup an lim sup +. Show from this, that the root test is stronger than the ratio test. That is,
More information1 More concise proof of part (a) of the monotone convergence theorem.
Math 0450 Honors intro to analysis Spring, 009 More concise proof of part (a) of the monotone convergence theorem. Theorem If (x n ) is a monotone and bounded sequence, then lim (x n ) exists. Proof. (a)
More information11.6: Ratio and Root Tests Page 1. absolutely convergent, conditionally convergent, or divergent?
.6: Ratio and Root Tests Page Questions ( 3) n n 3 ( 3) n ( ) n 5 + n ( ) n e n ( ) n+ n2 2 n Example Show that ( ) n n ln n ( n 2 ) n + 2n 2 + converges for all x. Deduce that = 0 for all x. Solutions
More informationFrom now on, we will represent a metric space with (X, d). Here are some examples: i=1 (x i y i ) p ) 1 p, p 1.
Chapter 1 Metric spaces 1.1 Metric and convergence We will begin with some basic concepts. Definition 1.1. (Metric space) Metric space is a set X, with a metric satisfying: 1. d(x, y) 0, d(x, y) = 0 x
More informationMATH 5640: Fourier Series
MATH 564: Fourier Series Hung Phan, UMass Lowell September, 8 Power Series A power series in the variable x is a series of the form a + a x + a x + = where the coefficients a, a,... are real or complex
More informationANALYSIS QUALIFYING EXAM FALL 2016: SOLUTIONS. = lim. F n
ANALYSIS QUALIFYING EXAM FALL 206: SOLUTIONS Problem. Let m be Lebesgue measure on R. For a subset E R and r (0, ), define E r = { x R: dist(x, E) < r}. Let E R be compact. Prove that m(e) = lim m(e /n).
More informationInternational Competition in Mathematics for Universtiy Students in Plovdiv, Bulgaria 1994
International Competition in Mathematics for Universtiy Students in Plovdiv, Bulgaria 1994 1 PROBLEMS AND SOLUTIONS First day July 29, 1994 Problem 1. 13 points a Let A be a n n, n 2, symmetric, invertible
More informationMath 163 (23) - Midterm Test 1
Name: Id #: Math 63 (23) - Midterm Test Spring Quarter 208 Friday April 20, 09:30am - 0:20am Instructions: Prob. Points Score possible 26 2 4 3 0 TOTAL 50 Read each problem carefully. Write legibly. Show
More informationTaylor and Maclaurin Series
Taylor and Maclaurin Series MATH 211, Calculus II J. Robert Buchanan Department of Mathematics Spring 2018 Background We have seen that some power series converge. When they do, we can think of them as
More information3 (Due ). Let A X consist of points (x, y) such that either x or y is a rational number. Is A measurable? What is its Lebesgue measure?
MA 645-4A (Real Analysis), Dr. Chernov Homework assignment 1 (Due ). Show that the open disk x 2 + y 2 < 1 is a countable union of planar elementary sets. Show that the closed disk x 2 + y 2 1 is a countable
More informationSummer Jump-Start Program for Analysis, 2012 Song-Ying Li
Summer Jump-Start Program for Analysis, 01 Song-Ying Li 1 Lecture 6: Uniformly continuity and sequence of functions 1.1 Uniform Continuity Definition 1.1 Let (X, d 1 ) and (Y, d ) are metric spaces and
More informationAustin Mohr Math 704 Homework 6
Austin Mohr Math 704 Homework 6 Problem 1 Integrability of f on R does not necessarily imply the convergence of f(x) to 0 as x. a. There exists a positive continuous function f on R so that f is integrable
More informationL p Functions. Given a measure space (X, µ) and a real number p [1, ), recall that the L p -norm of a measurable function f : X R is defined by
L p Functions Given a measure space (, µ) and a real number p [, ), recall that the L p -norm of a measurable function f : R is defined by f p = ( ) /p f p dµ Note that the L p -norm of a function f may
More informationNotes on uniform convergence
Notes on uniform convergence Erik Wahlén erik.wahlen@math.lu.se January 17, 2012 1 Numerical sequences We begin by recalling some properties of numerical sequences. By a numerical sequence we simply mean
More informationMath 409 Final Exam Solutions May 9, 2005
Math 49 Final Exam Solutions May 9, 25 1. 25) State and prove the monotone convergence theorem. Then use it to show that the recursive sequence defined below converges to some number l. What must l equal?
More informationMathematics 324 Riemann Zeta Function August 5, 2005
Mathematics 324 Riemann Zeta Function August 5, 25 In this note we give an introduction to the Riemann zeta function, which connects the ideas of real analysis with the arithmetic of the integers. Define
More informationGeneral Power Series
General Power Series James K. Peterson Department of Biological Sciences and Department of Mathematical Sciences Clemson University March 29, 2018 Outline Power Series Consequences With all these preliminaries
More informationBanach Spaces, HW Problems & Solutions from Hunter
Problem 1: Banach Spaces, HW Problems & Solutions from Hunter Ex 5.3: Let δ: C ([,1]) -> R be the linear functional that evaluates a function at the origin: δ(f ) = f (). If C ([,1]) is equipped with the
More informationUniform Convergence and Series of Functions
Uniform Convergence and Series of Functions James K. Peterson Department of Biological Sciences and Department of Mathematical Sciences Clemson University October 7, 017 Outline Uniform Convergence Tests
More informationSOLVED PROBLEMS ON TAYLOR AND MACLAURIN SERIES
SOLVED PROBLEMS ON TAYLOR AND MACLAURIN SERIES TAYLOR AND MACLAURIN SERIES Taylor Series of a function f at x = a is ( f k )( a) ( x a) k k! It is a Power Series centered at a. Maclaurin Series of a function
More informationExercises given in lecture on the day in parantheses.
A.Miller M22 Fall 23 Exercises given in lecture on the day in parantheses. The ɛ δ game. lim x a f(x) = L iff Hero has a winning strategy in the following game: Devil plays: ɛ > Hero plays: δ > Devil plays:
More informationMATH 131A: REAL ANALYSIS (BIG IDEAS)
MATH 131A: REAL ANALYSIS (BIG IDEAS) Theorem 1 (The Triangle Inequality). For all x, y R we have x + y x + y. Proposition 2 (The Archimedean property). For each x R there exists an n N such that n > x.
More informationWeak convergence. Amsterdam, 13 November Leiden University. Limit theorems. Shota Gugushvili. Generalities. Criteria
Weak Leiden University Amsterdam, 13 November 2013 Outline 1 2 3 4 5 6 7 Definition Definition Let µ, µ 1, µ 2,... be probability measures on (R, B). It is said that µ n converges weakly to µ, and we then
More informationMATH 140B - HW 5 SOLUTIONS
MATH 140B - HW 5 SOLUTIONS Problem 1 (WR Ch 7 #8). If I (x) = { 0 (x 0), 1 (x > 0), if {x n } is a sequence of distinct points of (a,b), and if c n converges, prove that the series f (x) = c n I (x x n
More informationDifferentiating Series of Functions
Differentiating Series of Functions James K. Peterson Department of Biological Sciences and Department of Mathematical Sciences Clemson University October 30, 017 Outline 1 Differentiating Series Differentiating
More informationMath 321 Final Examination April 1995 Notation used in this exam: N. (1) S N (f,x) = f(t)e int dt e inx.
Math 321 Final Examination April 1995 Notation used in this exam: N 1 π (1) S N (f,x) = f(t)e int dt e inx. 2π n= N π (2) C(X, R) is the space of bounded real-valued functions on the metric space X, equipped
More informationSection 5.8. Taylor Series
Difference Equations to Differential Equations Section 5.8 Taylor Series In this section we will put together much of the work of Sections 5.-5.7 in the context of a discussion of Taylor series. We begin
More informationMath 117: Continuity of Functions
Math 117: Continuity of Functions John Douglas Moore November 21, 2008 We finally get to the topic of ɛ δ proofs, which in some sense is the goal of the course. It may appear somewhat laborious to use
More informationTopics in Fourier analysis - Lecture 2.
Topics in Fourier analysis - Lecture 2. Akos Magyar 1 Infinite Fourier series. In this section we develop the basic theory of Fourier series of periodic functions of one variable, but only to the extent
More informationFINAL EXAM Math 25 Temple-F06
FINAL EXAM Math 25 Temple-F06 Write solutions on the paper provided. Put your name on this exam sheet, and staple it to the front of your finished exam. Do Not Write On This Exam Sheet. Problem 1. (Short
More informationREAL AND COMPLEX ANALYSIS
REAL AND COMPLE ANALYSIS Third Edition Walter Rudin Professor of Mathematics University of Wisconsin, Madison Version 1.1 No rights reserved. Any part of this work can be reproduced or transmitted in any
More informationFolland: Real Analysis, Chapter 8 Sébastien Picard
Folland: Real Analysis, Chapter 8 Sébastien Picard Problem 8.3 Let η(t) = e /t for t >, η(t) = for t. a. For k N and t >, η (k) (t) = P k (/t)e /t where P k is a polynomial of degree 2k. b. η (k) () exists
More informationMath 361: Homework 1 Solutions
January 3, 4 Math 36: Homework Solutions. We say that two norms and on a vector space V are equivalent or comparable if the topology they define on V are the same, i.e., for any sequence of vectors {x
More informationAnalysis III. Exam 1
Analysis III Math 414 Spring 27 Professor Ben Richert Exam 1 Solutions Problem 1 Let X be the set of all continuous real valued functions on [, 1], and let ρ : X X R be the function ρ(f, g) = sup f g (1)
More informationLimits at Infinity. Horizontal Asymptotes. Definition (Limits at Infinity) Horizontal Asymptotes
Limits at Infinity If a function f has a domain that is unbounded, that is, one of the endpoints of its domain is ±, we can determine the long term behavior of the function using a it at infinity. Definition
More informationDoubly Indexed Infinite Series
The Islamic University of Gaza Deanery of Higher studies Faculty of Science Department of Mathematics Doubly Indexed Infinite Series Presented By Ahed Khaleel Abu ALees Supervisor Professor Eissa D. Habil
More informationMATH 409 Advanced Calculus I Lecture 12: Uniform continuity. Exponential functions.
MATH 409 Advanced Calculus I Lecture 12: Uniform continuity. Exponential functions. Uniform continuity Definition. A function f : E R defined on a set E R is called uniformly continuous on E if for every
More informationMath Review for Exam Answer each of the following questions as either True or False. Circle the correct answer.
Math 22 - Review for Exam 3. Answer each of the following questions as either True or False. Circle the correct answer. (a) True/False: If a n > 0 and a n 0, the series a n converges. Soln: False: Let
More informationAP Calculus Chapter 9: Infinite Series
AP Calculus Chapter 9: Infinite Series 9. Sequences a, a 2, a 3, a 4, a 5,... Sequence: A function whose domain is the set of positive integers n = 2 3 4 a n = a a 2 a 3 a 4 terms of the sequence Begin
More informationTaylor and Maclaurin Series. Approximating functions using Polynomials.
Taylor and Maclaurin Series Approximating functions using Polynomials. Approximating f x = e x near x = 0 In order to approximate the function f x = e x near x = 0, we can use the tangent line (The Linear
More informationMath 209B Homework 2
Math 29B Homework 2 Edward Burkard Note: All vector spaces are over the field F = R or C 4.6. Two Compactness Theorems. 4. Point Set Topology Exercise 6 The product of countably many sequentally compact
More informationNumerical Analysis: Interpolation Part 1
Numerical Analysis: Interpolation Part 1 Computer Science, Ben-Gurion University (slides based mostly on Prof. Ben-Shahar s notes) 2018/2019, Fall Semester BGU CS Interpolation (ver. 1.00) AY 2018/2019,
More informationMetric Spaces. Exercises Fall 2017 Lecturer: Viveka Erlandsson. Written by M.van den Berg
Metric Spaces Exercises Fall 2017 Lecturer: Viveka Erlandsson Written by M.van den Berg School of Mathematics University of Bristol BS8 1TW Bristol, UK 1 Exercises. 1. Let X be a non-empty set, and suppose
More informationFrom Calculus II: An infinite series is an expression of the form
MATH 3333 INTERMEDIATE ANALYSIS BLECHER NOTES 75 8. Infinite series of numbers From Calculus II: An infinite series is an expression of the form = a m + a m+ + a m+2 + ( ) Let us call this expression (*).
More informationThus f is continuous at x 0. Matthew Straughn Math 402 Homework 6
Matthew Straughn Math 402 Homework 6 Homework 6 (p. 452) 14.3.3, 14.3.4, 14.3.5, 14.3.8 (p. 455) 14.4.3* (p. 458) 14.5.3 (p. 460) 14.6.1 (p. 472) 14.7.2* Lemma 1. If (f (n) ) converges uniformly to some
More informationSolutions to Homework #3, Math 116
Solutions to Homework #, Math 6 Keziah Cook and Michael McElroy November 5, Problem Goroff) In each of the following cases, determine the supremum of f over its domain D. If there are points x D for which
More informationProblem Set 2: Solutions Math 201A: Fall 2016
Problem Set 2: s Math 201A: Fall 2016 Problem 1. (a) Prove that a closed subset of a complete metric space is complete. (b) Prove that a closed subset of a compact metric space is compact. (c) Prove that
More informationTaylor and Maclaurin Series. Approximating functions using Polynomials.
Taylor and Maclaurin Series Approximating functions using Polynomials. Approximating f x = e x near x = 0 In order to approximate the function f x = e x near x = 0, we can use the tangent line (The Linear
More informationIntroduction to Real Analysis Alternative Chapter 1
Christopher Heil Introduction to Real Analysis Alternative Chapter 1 A Primer on Norms and Banach Spaces Last Updated: March 10, 2018 c 2018 by Christopher Heil Chapter 1 A Primer on Norms and Banach Spaces
More information