Question

Find the area of a regular decagon with radius 4 cm

Answer 1

$A = \frac{5}{2}t^{2} \sqrt{5 + 2 \sqrt{5} }$

$A = \frac{5}{2} (4)^{2} \sqrt{5 + 2(2.236067978)} }$

$A = \frac{5}{2} (16) \sqrt{5 + 4.472135956}$

$A = 40 \sqrt{9.472135956}$

$A = 40(3.077683537)$

$A = 123.1073415cm^{2}$

Answer 2

The area is 123.1073415 cm