中4數學題

sin^2 x + 2sinx cosx = 3cos^2 x
sin^2 x + 2sinx cosx - 3cos^2 x = 0
(sinx - cosx)(sinx + 3cosx) = 0
sinx = cos x or sinx = -3cosx
tanx = 1 or -3
x = 45, 225, 108.43, 288.43