# Math Help - Polar Double Integration help

1. ## Polar Double Integration help

I'm doing polar integration and I'm having some problems.

$4*\int_{0}^{\frac{\pi}{2}} \int_{0}^{1} ln(r^{2}+1)rdrd\theta$

$\pi(ln(4)-1)$ but I always end up with $\pi(ln(2)-1)$

2. Originally Posted by FalconPUNCH!
I'm doing polar integration and I'm having some problems.

$4*\int_{0}^{\frac{\pi}{2}} \int_{0}^{1} ln(r^{2}+1)rdrd\theta$

$\pi(ln(4)-1)$ but I always end up with $\pi(ln(2)-1)$
The only 'hard' bit is finding $\int_{1}^{2} \ln u \, du = 2 \ln (2) - 1$ where $u = r^2 + 1$. Note the integrals terminals (this is probably what you forgot).
The only 'hard' bit is finding $\int_{1}^{2} \ln u \, du = 2 \ln (2) - 1$ where $u = r^2 + 1$. Note the integrals terminals (this is probably what you forgot).