what is the answer of this indefinite integral? what is the answer of this indefinite integral? $$\int \frac{1}{x^{3}\cos^{2}(x)}dx$$
I have used all methods I knew, but all failed. some methods made it more complicated! please tell me your Ideas,that would be great.

Integrate by parts, using $\tan'(x)=\dfrac1{\cos^2x}$ . Then apply Liouville's theorem to $\displaystyle\int\frac{\tan x}{x^4}dx$ :-)
