
Kemal G. answered 05/25/17
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1) 4cosx*2sqrt(3) = 0
4cosx = 0
cosx = 0
x = {90, 270 deg}
2) 2sin^2x - sinx = 1
2sin^2x - sinx - 1 = 0
let sinx = u
2u^2 - u - 1 = 0
(2u + 1)(u - 1) = 0
2u + 1 = 0 or u - 1 = 0
u = -1/2 u = 1
sin x = -1/2
x = 210 and 330 deg
sin x = 1
x = 90
x={90, 210, 330 deg}
3) cos^2x = cosx
cos^2x - cosx = 0
cosx(cosx - 1) = 0
cosx = 0 or cosx = 1
x = 90 and 270 deg
cosx = 1
x = 0 and 360 deg
x={0, 90, 270 deg}