ini gimana caranya ... masih bingung mas mas mbak mbak

phi = 180°

a. sin 7x = sin 1/2phi
sin 7x = sin 90°
7x = 90°
x = 12,86°

b. cos 4x = cos 1/3phi
cos 4x = cos 60°
4x = 60°
x = 15°

c. tan 5x = tan 5/8phi
tan 5x = tan 56,25°
5x = 56,25°
x = 11,25°