Unit 9 Contents

9. Measure (or use shortcuts) to find the measures of the angles in the three Power Polygons™ below. Fill in a table like the one below to find the sums of the angles of those triangles.

1. Write a rule about the sum of the angles in a triangle.
2. Do you think the rule is true for every triangle? Explain your thinking.

The students in Mrs. Dewey's class answered Question 7 using their own triangles. Nila found the sum of the angles in her triangle to be 180°. When Romesh added the angles in his triangle, the sum was 179°. Ana's sum was 182°.

11. Why do you think the three students' measurements were different from each other?
12. Think about the kinds of angles that make up the 180 degrees in a triangle.
1. Can a triangle have all acute angles? If so, show an example.
2. Can a triangle have all right angles? More than one right angle? Show or tell how you know.
3. Can a triangle have more than one obtuse angle? Show or tell how you know.