Trigonometric substitution integral Trying to work around this with trig substitution, but end up with messy powers on sines and cosines... It should be simple use of trigonometric properties, but I seem to be tripping somewhere.
$$\int x^5\sqrt{x^2+4}dx $$
Thanks.

Put $x^2=t$. You will recieve $\frac{1}{2}\int t^2\sqrt{t+1}\mbox{d}t$. Now put $t+1=s$ and you will recieve $$\frac{1}{2}\int (s-1)^2\sqrt{s}\mbox{d}s.$$ That should be easy now.
