Problem:
Solve Cos(Pi/4-x), Given cos(x)=-1/6 & Pi/2
1) Simplify the given expression. Compute the exact answer as a fraction, it should not contain sin, cos, or tan.
cos((PI/4)-x), if cos(x)=-1/6 and PI/2 < x < PI
2) Use factoring, the quadratic formula, or identities to solve the given equation. Find the solution in the interval [0, 2*PI).
5 sin^2(x) + 3 sin (x) = 8