Question

sin22 and 1/2 = ........?

Answer 1

sin^2(22.5) = 1/2(1−cos(45))

sin^2(22.5) = 1/2(1−root 2/2) 

                 = 2−root 2/4

On squaring both sides, we get :

sin(22.5) = whole root 2− root 2/root 4= 0.382

sin(22.5) = 0.382

Answer 2

sin 22.5 = cos 67.5
cos 135 = 2 cos^2(67.5) - 1
0.0391216 = 2 cos^2(67.5)
cos^2(67.5) = 0.01956
cos(67.5) = 0.0442