tentukan hp dari 1. cos3x + 1/2√2 = √2, 0 < x < 360°

Persamaan Trigonometri

cos 3x + 1/2 √ 2 = √2 . , pada  0 < x < 360
cos 3x = √2 - 1/2√2 = - 1/2 √2 = - cos 45 = cos (180- 45) = cos 135
3x = 135 + k. 360  atau 3x = - 135 + k. 360
x = 45 + k. 120  atau x  = - 45 + k. 120
k = 0,1,2,3,4,...
k = 0 --> x = 45, x = - 45 (TM)
k = 1 --> x = 165 , x = 75
k = 2 --> x = 285 , x = 195
k = 3 -->x = 405 (TM) ,  x= 315

x = (45, 75, 165, 195, 185, 315)