3 sin x° + cos^2 x°-3 = 0

3sin x + cos²x - 3 = 0
3sin x + (1 - sin²x) - 3 = 0
3sin x + 1 - sin²x - 3 = 0
-sin²x + 3sin x - 2 = 0
sin²x - 3sin x + 2 = 0
(sin x - 2)(sin x - 1) = 0
sin x - 2 = 0
sin x = 2 (tidak memenuhi)
sin x - 1 = 0
sin x = 1
x = 90°