Question

How do you find the values of cos x and sin x when cox 2x is 1/8?

Answer 1

Cos x = +/- 3/4. Sin x = +/- √7/4

Explanation:

Cos (2x) = 2cos^2 (x) - 1 or 1 - 2sin^2 (x)

Cos 2x = 1/8
2 cos^2 (x) - 1 = 1/8
2 cos^2 (x) = 1 + 1/8 = 9/8
Cos^2 (x) = 9/16
Cos (x) = +/- 3/4

Similarly for sin (x)