Cos2x=1/2 akar 3 untuk 0<×>180

cos 2x = 1/2√3
cos 2x = cos 30
2x1 = 30 + k.360
x1 = 15 + k.360
k = 0 → x = 15
2x2 = -30 + k.360
x2 = -15 + k.360
k = 1 → x = 345

HP {15}