What is the measure of ONE interior angle in a regular triangle (3 sides)?

Acircle has a circumference of 28.36 units what is the diameter of the circle

In the figure below, ∠dec ≅ ∠dce, ∠b ≅ ∠f, and segment df is congruent to segment bd. point c is the point of intersection between segment ag and segment bd, while point e is the point of intersection between segment ag and segment df. the figure shows a polygon comprised of three triangles, abc, dec, and gfe. prove δabc ≅ δgfe.

Pranza plotted point a in the coordinate plane below.