4/5/MATHL/HP/ENG/TZ/XX/M MARKSCHEME May 04 MATHEMATICS Higher Level Paper 4 pages
4/5/MATHL/HP/ENG/TZ/XX/M This markscheme is confidential and for the exclusive use of examiners in this examination session. It is the property of the International Baccalaureate and must not be reproduced or distributed to any other person without the authorization of the IB Assessment Centre.
4/5/MATHL/HP/ENG/TZ/XX/M Instructions to Examiners Abbreviations M (M) A (A) R N AG Marks awarded for attempting to use a correct Method; working must be seen. Marks awarded for Method; may be implied by correct subsequent working. Marks awarded for an Answer or for Accuracy; often dependent on preceding M marks. Marks awarded for an Answer or for Accuracy; may be implied by correct subsequent working. Marks awarded for clear Reasoning. Marks awarded for correct answers if no working shown. Answer given in the question and so no marks are awarded. Using the markscheme General Mark according to Scoris instructions and the document Mathematics HL: Guidance for e-marking May 04. It is essential that you read this document before you start marking. In particular, please note the following: Marks must be recorded using the annotation stamps. Please check that you are entering marks for the right question. If a part is completely correct, (and gains all the must be seen marks), use the ticks with numbers to stamp full marks. If a part is completely wrong, stamp A0 by the final answer. If a part gains anything else, it must be recorded using all the annotations. All the marks will be added and recorded by Scoris. Method and Answer/Accuracy marks Do not automatically award full marks for a correct answer; all working must be checked, and marks awarded according to the markscheme. It is not possible to award M0 followed by, as A mark(s) depend on the preceding M mark(s), if any. Where M and A marks are noted on the same line, eg, this usually means for an attempt to use an appropriate method (eg substitution into a formula) and for using the correct values. Where the markscheme specifies (M), N, etc., do not split the marks. Once a correct answer to a question or part-question is seen, ignore further working. N marks Award N marks for correct answers where there is no working. Do not award a mixture of N and other marks. There may be fewer N marks available than the total of M, A and R marks; this is deliberate as it penalizes candidates for not following the instruction to show their working.
4 4/5/MATHL/HP/ENG/TZ/XX/M 4 Implied marks Implied marks appear in brackets eg (), and can only be awarded if correct work is seen or if implied in subsequent working. Normally the correct work is seen or implied in the next line. Marks without brackets can only be awarded for work that is seen. 5 Follow through marks Follow through (FT) marks are awarded where an incorrect answer from one part of a question is used correctly in subsequent part(s). To award FT marks, there must be working present and not just a final answer based on an incorrect answer to a previous part. If the question becomes much simpler because of an error then use discretion to award fewer FT marks. If the error leads to an inappropriate value (eg sinθ.5 ), do not award the mark(s) for the final answer(s). Within a question part, once an error is made, no further dependent A marks can be awarded, but M marks may be awarded if appropriate. Exceptions to this rule will be explicitly noted on the markscheme. 6 Mis-read If a candidate incorrectly copies information from the question, this is a mis-read (MR). A candidate should be penalized only once for a particular mis-read. Use the MR stamp to indicate that this has been a misread. Then deduct the first of the marks to be awarded, even if this is an M mark, but award all others so that the candidate only loses one mark. If the question becomes much simpler because of the MR, then use discretion to award fewer marks. If the MR leads to an inappropriate value (eg sinθ.5), do not award the mark(s) for the final answer(s). 7 Discretionary marks (d) An examiner uses discretion to award a mark on the rare occasions when the markscheme does not cover the work seen. In such cases the annotation DM should be used and a brief note written next to the mark explaining this decision. 8 Alternative methods Candidates will sometimes use methods other than those in the markscheme. Unless the question specifies a method, other correct methods should be marked in line with the markscheme. If in doubt, contact your team leader for advice. Alternative methods for complete questions are indicated by METHOD, METHOD, etc. Alternative solutions for part-questions are indicated by EITHER... OR. Where possible, alignment will also be used to assist examiners in identifying where these alternatives start and finish.
5 4/5/MATHL/HP/ENG/TZ/XX/M 9 Alternative forms Unless the question specifies otherwise, accept equivalent forms. As this is an international examination, accept all alternative forms of notation. In the markscheme, equivalent numerical and algebraic forms will generally be written in brackets immediately following the answer. In the markscheme, simplified answers, (which candidates often do not write in examinations), will generally appear in brackets. Marks should be awarded for either the form preceding the bracket or the form in brackets (if it is seen). Example: for differentiating f () x sin(5x ), the markscheme gives: ( ) ( cos(5 ) ) 5 ( 0cos(5x ) ) f x x Award for ( cos(5x ) ) 5, even if 0cos(5x ) is not seen. 0 Accuracy of Answers Candidates should NO LONGER be penalized for an accuracy error (AP). If the level of accuracy is specified in the question, a mark will be allocated for giving the answer to the required accuracy. When this is not specified in the question, all numerical answers should be given exactly or correct to three significant figures. Please check work carefully for FT. Crossed out work If a candidate has drawn a line through work on their examination script, or in some other way crossed out their work, do not award any marks for that work. Calculators No calculator is allowed. The use of any calculator on paper is malpractice, and will result in no grade awarded. If you see work that suggests a candidate has used any calculator, please follow the procedures for malpractice. Examples: finding an angle, given a trig ratio of 0.45. More than one solution Where a candidate offers two or more different answers to the same question, an examiner should only mark the first response unless the candidate indicates otherwise. 4. Candidate work Candidates are meant to write their answers to Section A on the question paper (QP), and Section B on answer booklets. Sometimes, they need more room for Section A, and use the booklet (and often comment to this effect on the QP), or write outside the box. This work should be marked. The instructions tell candidates not to write on Section B of the QP. Thus they may well have done some rough work here which they assume will be ignored. If they have solutions on the answer booklets, there is no need to look at the QP. However, if there are whole questions or whole part solutions missing on answer booklets, please check to make sure that they are not on the QP, and if they are, mark those whole questions or whole part solutions that have not been written on answer booklets.
6 4/5/MATHL/HP/ENG/TZ/XX/M SECTION A. (a) P( A B) P( A B) P( B) P( A B) 0 () 0 (b) P( A B) P( A) + P( B) P( A B) P( A B) + 5 0 0 () 7 0 [ marks] [ marks] (c) No events A and B are not independent EITHER P( A B) P( A) R 5 OR P( A) P( B) P( A B) R 5 0 50 0 Note: The numbers are required to gain R in the OR method only. Note: Do not award R0 in either method. [ marks] Total [6 marks]
7 4/5/MATHL/HP/ENG/TZ/XX/M. METHOD ( x ) x ( ) Note: Award for writing in terms of and. x x x x ln ln x () ( ) ( ) ln xln ln x ln METHOD x ln8 x ln 6 () ( x )ln xln( ) xln ln xln + xln ln x ln METHOD x ln8 x ln 6 () ( x )ln8 xln6 ln8 x ln8 ln 6 ln x ln 6 ln x ln Total [5 marks]
8 4/5/MATHL/HP/ENG/TZ/XX/M. (a) EITHER 4 6 0 0 5 0 0 0 0 row of zeroes implies infinite solutions, (or equivalent). R Note: Award for any attempt at row reduction. OR 4 0 0 4 0 with one valid point R 0 OR x+ y+ z x y+ 4z 6 x+ y 5 x 5 y substitute x 5 y into the first two equations: 5 y+ y+ z ( 5 y) y+ 4z 6 y+ z 7y+ 4z the latter two equations are equivalent (by multiplying by 7) therefore an infinite number of solutions. R OR for example, 7 R R gives 4x+ 8y 0 this equation is a multiple of the third equation, therefore an infinite number of solutions. R continued
9 4/5/MATHL/HP/ENG/TZ/XX/M Question continued (b) let y t then x 5 t t + z OR let x t 5 t then y t z 4 OR let z t then x 4t y + t OR attempt to find cross product of two normal vectors: i j k eg: 4i+ j+ k 0 x 4t y + t z t (or equivalent) Total [5 marks]
0 4/5/MATHL/HP/ENG/TZ/XX/M 4. (a) using the formulae for the sum and product of roots: α + β αβ α + β ( α+ β) αβ ( ) 5 [4 marks] Note: Award M0 for attempt to solve quadratic equation. (b) ( x )( x ) x ( ) x x x α β α + β + α β 5x+ 0 5x+ 0 4 Note: Final answer must be an equation. Accept alternative correct forms. [ marks] Total [6 marks] 5. (a) Note: Award for correct shape and for correct domain and range. [ marks] continued
4/5/MATHL/HP/ENG/TZ/XX/M Question 5 continued (b) x cos 4 4 x attempting to find any other solutions Note: Award () if at least one of the other solutions is correct (in radians or degrees) or clear use of symmetry is seen. 4 0 x 8 4 8 x 4 4 6 x 4+ Note: Award for all other three solutions correct and no extra solutions. Note: If working in degrees, then max A0A0. [ marks] Total [5 marks] 6. (a) PR a+ b QS b a [ marks] (b) PR QS ( a+ b) ( b a ) b a for a rhombus a b R hence b a 0 Note: Do not award the final unless R is awarded. hence the diagonals intersect at right angles AG [4 marks] Total [6 marks]
4/5/MATHL/HP/ENG/TZ/XX/M 7. (a) METHOD i i + + + i + i 4+ 9 9+ 4 0 5 5i w 0 w 5 5i 0 5 ( + i) 50 w + i METHOD + i+ + i + + i + i (+ i)(+ i) 0 5 + 5i w i w i 0 5 + 5i 0i (5 5i) w (5 + 5i) (5 5i) 650 + 650i 50 + i [4 marks] [4 marks] (b) w i i i 4 4 z 8e e 7 Note: Accept θ. 4 Do not accept answers for θ given in degrees. [ marks] Total [7 marks]
4/5/MATHL/HP/ENG/TZ/XX/M 8. (a) () and ( ) 4 both answers are the same, hence f is continuous (at x ) R Note: R may be awarded for justification using a graph or referring to limits. Do not award A0R. [ marks] (b) reflection in the y-axis + x, x f ( x) ( ) x+, x< 4 () Note: Award for evidence of reflecting a graph in y-axis. translation 0 x, x 0 g( x) x, x< 0 4 () Note: Award () for attempting to substitute ( x ) for x, or translating a graph along positive x-axis. Award for the correct domains (this mark can be awarded independent of the ). Award for the correct expressions. [4 marks] Total [6 marks]
4 4/5/MATHL/HP/ENG/TZ/XX/M 9. (a) sin x, sinx and 4sin xcos x sin xcos x r cos x sin x Note: Accept sin x sin x. [ mark] (b) EITHER r < cosx < OR < r < < cos x< THEN 0< cosx < for < x < < x < or < x < [ marks] (c) S sin x cos x sin arccos 4 S cosarccos 4 5 4 Note: Award for correct numerator and for correct denominator. 5 AG [ marks] Total [7marks]
5 4/5/MATHL/HP/ENG/TZ/XX/M 0. x asecθ dx sec tan dθ () new limits: x a θ and x a θ 4 () asecθtanθ 4 a sec θ a sec θ a dθ cos θ d θ a 4 using cos θ ( cosθ ) a + sin θ + θ 4 or equivalent + or equivalent 4a ( + 6) 4a AG [7 marks] Total [7 marks]
6 4/5/MATHL/HP/ENG/TZ/XX/M SECTION B. (a) (i) Note: Award for a correctly labelled tree diagram and for correct probabilities. (ii) P( F ) 0.6 0.0+ 0.4 0.0 () 0.06 (iii) P( A F) P( A F) P( F) 0.6 0.0 0.0 0.06 0.06 0.75 [6 marks] continued
7 4/5/MATHL/HP/ENG/TZ/XX/M Question continued (b) (i) METHOD C C P( X ) () 4 7 C 5 METHOD 4 7 6 5 () 5 (ii) x 0 4 8 P( X x) 5 5 5 5 A Note: Award if 4 5, 8 5 or 5 is obtained. (iii) E( X) xp( X x) 4 8 E( X ) 0 + + + 5 5 5 5 45 9 5 7 [6 marks] Total [ marks]
8 4/5/MATHL/HP/ENG/TZ/XX/M. (a) direction vector AB or BA 5 5 r 0 + t or r + t or equivalent 4 5 5 Note: Do not award final unless r K (or equivalent) seen. Allow FT on direction vector for final. [ marks] (b) both lines expressed in parametric form: L : x + t y t z 4 5t L : x + s y + s z s+ Notes: Award for an attempt to convert L from Cartesian to parametric form. Award for correct parametric equations for L and L. Allow at this stage if same parameter is used in both lines. attempt to solve simultaneously for x and y : + t + s t + s t, 4 s 4 substituting both values back into z values respectively gives and z so a contradiction R L are skew lines AG therefore L and z 4 [5 marks] continued
9 4/5/MATHL/HP/ENG/TZ/XX/M Question continued (c) finding the cross product: 5 () i j 8k Note: Accept i+ j+ 8k (0) () 8( ) () x y 8z or equivalent [4 marks] (d) (i) ( cosθ ) k k 0 + + + Note: Award for an attempt to use angle between two vectors formula. k + ( k + ) obtaining the quadratic equation 4( k+ ) 6( k + ) k 4k+ 4 0 ( k ) 0 k Note: Award A0A0 if cos60 o is used ( k 0 or k 4). continued
0 4/5/MATHL/HP/ENG/TZ/XX/M Question continued (ii) r 0 λ + substituting into the equation of the plane Π : + λ+ λ λ point P has the coordinates: (9,, ) 9 Notes: Accept 9i+ j k and. Do not allow FT if two values found for k. [7 marks] Total [8 marks]. (a) ( x ) x x x x ( x + ) ( x + ) + ( + ) + f ( x) [ marks] (b) x x+ ( x + ) 0 x ± [ mark] continued
4/5/MATHL/HP/ENG/TZ/XX/M Question continued (c) f ( x) ( x )( x + ) ( x)( x + )( x x+ ) 4 ( x + ) ( ) ( ) ( x + ) ( x ) x + 4x x x+ x + 6x 6x ( x + ) ( x + x x ) ( x + ) ( x ) x + or equivalent. Note: Award for ( ) Note: Award for ( x) ( x )( x x ) + + or equivalent. [ marks] (d) recognition that ( x ) is a factor (R) ( ) ( ) ( x ) x + bx+ c x + x x x + 4x+ 0 x ± (e) Note: Allow long division / synthetic division. 0 x + d x x + x+ x dx dx+ dx x + x + x + ln ( x + ) + arctan( x ) 0 ln( x + ) + arctan( x) ln+ arctan 0 ln arctan( ) ln 4 [4 marks] [6 marks] Total [6 marks]
4/5/MATHL/HP/ENG/TZ/XX/M 4. (a) Note: for correct shape, for asymptotic behaviour at y ±. [ marks] (b) ho g( x) arctan x domain of ho g is equal to the domain of g : x, x 0 [ marks] (c) (i) f ( x) arctan( x) + arctan x f ( x) + + x + x x f ( x) + x () + x x + x + x + x 0 continued
4/5/MATHL/HP/ENG/TZ/XX/M Question 4 continued (ii) METHOD f is a constant R when x > 0 f () + 4 4 AG METHOD from diagram θ arctan x α arctan x θ + α R hence f( x) AG METHOD tan ( f ( x) ) tanarctan( x) + arctan x x + x x x denominator 0, so f( x ) (for x > 0 ) R [7 marks] continued
4 4/5/MATHL/HP/ENG/TZ/XX/M Question 4 continued (d) (i) Nigel is correct. METHOD arctan( x ) is an odd function and is an odd function x composition of two odd functions is an odd function and sum of two odd functions is an odd function R METHOD f ( x) arctan( x) + arctan arctan( x) arctan f ( x) x x therefore f is an odd function. R (ii) f ( x) [ marks] Total [4 marks]