# Inverse of $x^2+\log^2\cos x$

I'm looking for the inverse of

$$f(x)=x^2+(\log\cos x)^2$$

Where $f$ is defined from $[0,\pi/2)$

It dosen't have to be closed form, a sum, an integral or some special functions would be of interest too.

• Have you tried anything? – Mhenni Benghorbal Sep 1 '14 at 4:56
• @MhenniBenghorbal I tried WA and sagemath, but none of them can solve it, and I know no theorems I can use. – Alice Ryhl Sep 1 '14 at 4:58
• Where did this problem come from? – Mhenni Benghorbal Sep 1 '14 at 5:04
• @MhenniBenghorbal From this post, read the comments of the post – Alice Ryhl Sep 1 '14 at 5:12