How to integrate $\int \frac{1}{\sin^4(x)\cos^4(x)}\,\mathrm dx$? How can I integrate $$\int \frac{1}{\sin^4(x)\cos^4(x)}\,\mathrm dx.$$
So I know that for this one we have to use a trigonometric identity or a substitution. Integration by parts is probably not going to help. Can someone please point out what should I do to evaluate this integral?  
Thanks!

Hint: Substitute $t=\tan x$.

 Then $\frac{dx}{\sin^4 x \cos^4 x} = \frac{(1+t^2)^3}{t^4}dt$.

