Algebra
posted by Cassie .
What is the measure of each of the interior angles of these regular polygons?
a) pentagon
b) octagon
c) dodecagon
How would I figure this out?

add up the exterior angles between the extension of one side and the next side.
They must add up to 360 because they go all the way around.
Then the interior angle is the supplement.
For example for a regular pentagon
exterior between side extension and side = 360/5 = 72
so each interior angle is
180  72 = 108