Question

Here is a regular pentagon.

Calculate the size of the interior angle marked c.
C
Co

Answer 1

c = 108°

Explanation:

the sum of the interior angles of a polygon is

sum = 180° (n - 2) ← n is the number of sides

here n = 5 , then

sum = 180° × (5 - 2) = 180° × 3 = 540°

since the pentagon is regular then the 5 interior angles are congruent, so

c = 540° ÷ 5 = 108°