Question

15. Find all solutions to 2cos² (x) - 7cos(x) +3=0​

Answer 1

Explanation:

2cos²x-7cosx+3=0

2cos²x-6cosx-cosx+3=0

2cosx(cosx-3)-1(cosx-3) =0

cosx=3, 1/2

cosx =3 is rejected as range of cosx lies between [-1, 1]

so cosx=1/2 is the only solution of the given equatiom

Answer 2

Answer: x=π/3+2πn, 5π/3+2πn, for any integer n