Any Ideas on how to Approach this one? ...

$\displaystyle \int\sqrt{[1-sech(u)]^{2}+ [-tanh(u)sech(u)]^{2}}du$

We have a $\displaystyle sech(u)$ and its derivative $\displaystyle -tanh(u)sech(u)$ and this suggests some sort of substitution maybe, but the radical makes it a bit nasty for Me.

Any Ideas? ...Thanks Heaps,