bagaimana caranya ya??

Persamaan Trigonometri

4 sin (x - 30) = cos x
4 [ sin x cos 30 - cos x sin 30] = cos x
4 [ sin x (1/2 √3 - cos x (1/2) ] = cos x
2√ 3 sin x - 2 cos x = cos 
2√3 sin x= 3 cos x
sin x = 3/(2√3) cos x --> bagikan dgn cos x
.
sin x / cos x = 1/2 √3 
tan x = 1/2 √3  --> x = tan⁻¹ (1/2 √3) = tan 40,89
x1 = 40, 89
x2= (180 + 40,89) = 220,89

x = {( 40, 89), (220,89) }