Solve for x:

3sin^2(x)=cos^2(x) ; 0≤x≤2π

3sin^2 x - cos^2 x = 0

3sin^2x - (1- sin^2 x) = 0
4sin^2 x = 1
sin^2 x = 1/4
sinx = ± 1/2

So x could in in all 4 quadrants,
(30°, 150°, 210°, and 330°)

x =π/6, 5π/6, 7π/6. and 11π/6