(1-cosx)(4+3cos2x)=0

Question

(1-cosx)(4+3cos2x)=0

Answer 1

1-cosx=0

cosx=1

x=pi+2pin.

cos2x=-4/3

2x=+- (pi - arccos4/3) + 2pin

x=+-1/2pi- 1/2 arccos4/3 = pin