### Home > GC > Chapter 9 > Lesson 9.2.2 > Problem9-72

9-72.

Which has greater measure: an exterior angle of an equilateral triangle or an interior angle of a regular heptagon ($7$-gon)? Show all work.

Remember that the sum of all exterior angles is equal to $360°$.

$\frac{360^◦}{3}=120^◦\text{ for each exterior angle, since it is an equilateral triangle.}$

$\text{Measure of one interior angle }=\frac{(n-2)(180)}{n}$

Substitute $7$ for $n$ and determine which of the two angles has a greater measure.