Question

A regular decagon has side lengths of 4 centimeters long. If the decagon is divided into 10 congruent triangles, each has an approximate height of 6.2 centimeters. What is the approximate are of the decagon?

Answer 1

$A = \frac{5}{2} a^2 \sqrt{5 + 2 * \sqrt{5} }$
a=side length
$A = \frac{5}{2} (4)^2 \sqrt{5 + 2 * \sqrt{5} }$