express the angular measurement of angle of a regular decagon in degree grades and radian

Answer 1

ten sides?
going around the outside we have to turn right ten times
that means each time we turn right 36 degrees which is 360/10
that means the interior angle= 180 - 36 = 144 degrees

in radians this is pi - 2pi/10
= 5 pi/5 - pi/5 = 4 pi/5