1. Lesson 3.5 AIM: The Polygon Exterior Angle Sum Theorem
Do Now: Find the measure of Angle A.
Step 1: How many sides in the shape?
5 sides
Step 2: Sum of Interior Angles?
(n - 2)180
(5 - 2)180 = 540º
Step 3: Subtract Given Angles.
= 127º

2. The sum of the measures of the exterior angles in a polygon is
360º

3. The sum of an exterior and interior angle is
180º

4. Find the value of x. The sum of exterior angles = 360º
x + 2x = 360
3x = 360
3x = 180
x = 60º

5. Find the number of sides of the regular polygon with the exterior angle measure of 60º.
a. What is the measure of one of the interior angles?
= 120º
Use the polygon exterior angle theorem to find the number of sides.
360º ÷ 60º
= 6 sides

6. Summary Question