standard_description: Derive using similarity the fact that the length of the arc intercepted by an angle is proportional to the radius, and define the radian measure of the angle as the constant of proportionality; derive the formula for the area of a sector.
problem_activity: Task
Materials
Double sided counters
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Markers that are the same colors as the counters
Teacher-made “My Book of 5” (see below for detailed directions)
Action
Students will be given double sided counters/dots (see picture of counters, above). It is important for the markers to match the colors on the counters. Students take five counters in their cupped hands (or a cup), shake them around, pour them onto the desk. Next, they count how many counters are yellow and how many are red. Students then record the numbers in their book and write a corresponding equation. For example, if the counters landed so that 1 was yellow and 4 were red, then the student would draw one yellow dot and four red dots and then write “1+4=5” under the drawing. The student would then collect the counters and roll them again. For each combination of colors, the students record with a picture and an equation. Students continue until they fill their book of 5. The teacher can choose how many pages to put in, somewhere between five and eight is a good number so that students get a chance to see multiple combinations. After the students have completed their books, the teacher should have a whole-group discussion to make the number relationships explicit. One way to do this is to write each of the two addends into a table and to discuss possible patterns and reasons for the pattern. The teacher can ask specific questions such as, “What do you notice about the numbers in the table?” Or “Why is it that as one number gets bigger, the other number gets smaller?”
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Once students have completed the book, the activity can be repeated but with a book that has 6 pages. The students would then need to create one page for each possible way to make five. How to make "My Book of 5": The book could simply be blank pages stapled together and the student creates the circle and writes the equation under. If your students need more scaffolding each page of the book can consist of five empty circles which the students color in. This will make it impossible for the students to accidentally draw four or six circles. See below for an example: Empty Book Pages:
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Filled In by Student:
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Here is a photo of students working on different numbered books (not books of five):
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