Question

Question #88e13

Answer 1

x = arc sin (( 1 `+-` `sqrt`17/8))
= 39.82 deg and 337.02 deg, nearly, in [0, 2`pi`] .

Explanation:

Use cos (2#x) = 1 - 2 sin(x).sin(x).
Solve the resulting quadratic equation in sin(x).,