#### Hckyplayer8

##### Full Member

- Joined
- Jun 9, 2019

- Messages
- 269

Hello. I was working on this problem and got stuck after converting the integral to polar coordinates and integrating theta. Because the function converts to r^2

the integral becomes

My question involves the next step which tells me to assume [math]1+4r^2=t[/math]

My question is, why? Is this just an arbitrary variable that just so happens to be t? Or does it mean more?