Question

Need help!! Answers are
A. 0, 5pi/4
B. 7pi/6, 11pi/6
C. 3pi/4, 7pi/4
D. Pi/4, 5pi/4

Answer 1

1−cos2θ/cos2θ=−3/2⋅1/cosθ

2(1−cos2θ)= −3cos θ and cosθ≠0

2−2cos2θ+3cosθ=0 and cosθ≠0

2cos2θ−3cosθ−2=0 and cosθ≠0

cosθ=3±√9+16/4 and cosθ≠0

cosθ=3±5/4 and cosθ≠0

cosθ=−1/2;cosθ=2andcosθ≠0

so the answer is 

θ=2pie /3and θ=4π/ 3