Solve the Trigo. equation

1 - 6tan^2 X + 4sin^2 X = 0

cos^2 X - 6sin^2 X + 4sin^2 X cos^2 X = 0

(1 - sin^2 X) - 6sin^2 X + 4sin^2 X (1 - sin^2 X) = 0

4sin^2 X + 3sin^2 X - 1 = 0

(4sin^2 X - 1)(sin^2 X + 1) = 0

sin X = 1/2 or sin X = -1/2 or sin X = 1 or sin X = -1

X = 30, 150, 210, 330, 90, 270

2011-05-15 10:26:38 補充：
Please delete 90 and 270.