Problem involving double cosine: 3cos(2θ) = -1.6 0 ≤ θ ≤ π

[Bazoya]

Solve the following for θ:

3cos(2θ) = -1.6 0 ≤ θ ≤ π

If any help on how to solve a problem such as this that would be great.
Thanks
Bazoya

 

[pka]

Solve the following for θ:
3cos(2θ) = -1.6 0 ≤ θ ≤ π

Does this help?