(tambahan POIN) Himpunan penyelesaian dari cos (x - 30)° = Sin 2x untuk 0°≤x≤360° adalah....

cos (x-30) = sin 2x
sin(90 - (x-30)) = sin 2x
sin (90-x+30) = sin 2x
sin (120-x) = sin 2x
120 - x = 2x
120 = 2x + x
120 = 3x
x = 120/3 = 40
sin (360+120-x) = sin 2x
360 + 120 - x = 2x
480 = 2x + x
480 = 3x
x = 480/3 = 160
sin (720+120-x) = sin 2x
720 + 120 - x = 2x
840 = 2x + x
840 = 3x
x = 840/3 = 280
hp {40° 160° 280°}