Display the following sentence: The principal said she would never agree to an ice cream social, but then she. Students play.

Transcription

1 1 Lesson Plan Angle Measures Age group: 4 t h Grade, 5 t h Grade Mathematics Syllabus Primary : 4.G.A.2, 4.G.A.4, 5.F M - G.A.2, 5.F M - G.A.4 Online resources: What ' s Yo ur Angl e? Opening Teacher present s Students play Class discussion Closing GOAL S: E xpe ri e nc e manipulating sectors within a circle P rac t i c e finding the measure of an angle Learn to identify acute, right, obtuse, and straight angles De vel o p geometry skills Ope ni ng 7 Display the following sentence: The principal said she would never agree to an ice cream social, but then she

2 2 did a 180. Ask the students to talk in pairs. Ask: In this sentence, what does did a 180 mean? When the students have talked in their pairs for a ute, share. Ask: In this sentence, what does did a 180 mean? It means to change her d entirely or to do the opposite. It means the principal agreed to the ice cream social. Say: The expression comes from the fact that a circle contains 360 degrees. So if you make a 360 degree turn, you have come full circle, turned around one full revolution, and arrived back at your original ideas. But to do a 180 is to turn 180 degrees, which means that your ideas are the opposite of what they once were. So what does a 180 degree turn look like? A 180 degree turn is to turn halfway around so that you are facing the opposite direction. Display the following: Say: We can cut the circle up further into smaller wedges. Rather than making a 180 degree turn, we could make a quarter turn, or 90 degree turn. This is called a rir i ght angl e. Write on the board: Right a ngle a 90 degree angle (a quarter turn) A c ut e a ngle an angle between 0 and 90 degrees

3 3 Obt us e a ngle an angle between 90 and 180 degrees S t ra ight a ngle a 180 degree angle T e ac he r prese nt s What s Yo ur Angl e? 12 Present Matific s episode What s Yo ur Angl e? - Quant i f yi ng P art s o f a Ci rc l e to the class, using the projector. The goal of the episode is to detere the measure of an angle by detering how many sectors fit in a circle. Example : Say: The episode wants us to detere the measure of the given angle. Let s see how many wedges fit inside the circle. Move the sector onto the circle. Continue placing sectors onto the circle until the circle is completely covered. Ask: How many wedges does it take to cover the circle? Students can answer based on the episode. Ask: How do we detere the measure of angle A? How do you know? We divide 360 by the number of times that the wedge fits inside the circle. The measure of the whole circle is 360 degrees, so we

4 4 divide to find the angle of each piece. Ask: So what is the measure of angle A? Students can do the division to calculate the answer. Click on the to enter the value that the students offer. If the answer is correct, the episode will demonstrate the division involved in the problem. If the answer is incorrect, the question will wiggle. Ask: Is angle A acute, right, or obtuse? Students can answer based on the episode. Click on the to proceed to the next question. The episode will present a total of six questions. St ude nt s pl ay What s Yo ur Angl e? 15 Have the students play What s Yo ur Angl e? - Quant i f yi ng P art s o f a Ci rc l e on their personal devices. Students should also have time to play What s Yo ur Angl e? - N ami ng Angl e s. Circulate, answering questions as necessary. Cl ass di sc ussi o n 10 Display the following:

5 5 Ask: What kind of angle is made by the hands of the clock? The hands of the clock form a right angle. Ask: Is three o clock the only right angle that can be made with the hands of the clock? No. A right angle occurs at nine o clock also. We can make other right angles, too, such as 4:05. (Of course, to be precise, the hour hand may have moved slightly away from the 4 at 4:05.) Ask: If we place the hour hand on one number of the clock and the ute hand on the next number (see diagram below), what is the measure of the angle formed? How do you know? The angle measures 30 degrees. Since there are 360 degrees in a circle and the clock is divided into 12 sections, we divide 360 by 12 to get 30. Ask: How could we make a 120 degree angle? How do you know? Responses may vary. A possible response: At 4:00, a 120 degree angle occurs. The ute hand is on the 12 and the hour hand is on

6 6 the 4. The measure between consecutive numbers is 30 degrees. So we have 4 sets of 30 degrees from 12 to 4. Four sets of 30 is 120 degrees. Ask: Is this the only way to make a 120 degree angle? No. Any time the two hands are four numbers apart on the clock, a 120 degree angle is formed. Ask: What kind of angle is a 120 degree angle? It is an obtuse angle. Display the following: Ask the students to copy and complete the table. They should complete the table by writing the times from the box in the correct column. They should consider the angle formed between the hands of the clock. (No reflex angles should be considered.) Review answers.

7 7 Cl o si ng 3 Ask: True or False? A 360 degree turn is a half revolution. False. A 360 degree turn is a full revolution. Ask: True or False? An acute angle is smaller than a right angle. True. An acute angle is smaller than a right angle. Ask: True or False? Two identical acute angles next to each other could form a right angle. True. Two 45 degree angles together form a right angle. Ask: True or False? Two obtuse angles next to each other form a straight angle. False. Two right angles together form a straight angle.