How do I find the inverse of a $\cos^2 \theta$? This was originally a physics question, but the math is what is throwing my brain into loops.
Basically, I need to find $\theta$:
$$
\frac{7}{8}= \cos^2(\theta)
$$

Hint: $\displaystyle \cos^2 \theta = \frac{7}{8}$ simply means that $\displaystyle \cos \theta = \pm\sqrt{\frac{7}{8}}$. Can you take it from there? The answer will not be a multiple of $\pi$ (assuming you're using radians).
