Question 1170384
Using the identity sin^2x + cos^2x = 1, we have:
1 - cos^2x = 3cos^2x -> 1 = 4cos^2x -> cos^2x = 1/4
Thus, we need to find x such that cosx = +-1/2.
In the 2nd quadrant, cos(120) = -1/2
In the 3rd quadrant, cos(240) = -1/2