I'm trying to solve the following integral:
{ stands for integral
{x^3/(sqrt[x^2 +4]) dx
This is what I have so far:
@ stands for pheta
x=2tan@
dx=2sec^2@ d@
x^2+4=4(1+tan^2@)
Sqrt[x^2+4]=2sec@
Plugging it back in:
{8tan^3@2sec^2@/2sec@ d@
which simplifies to
8{tan^3@sec@ d@
I can't seem to solve this. I've tried integration by parts as well as simple sub.
Where am I going wrong?
Thank you!!