- #1
8614smith
- 54
- 0
Homework Statement
By transforming to polar coordinates, evaluate the following:
[tex]\int^{a}_{-a}\int^{\sqrt{}{{a^2}-{x^2}}}_{-\sqrt{{a^2}-{x^2}}}dydx[/tex]
Homework Equations
The Attempt at a Solution
I can get the right answer to this but only after guessing that the inner limits are between 0 and a, and the outer limits are between 0 and [tex]2\pi[/tex].
Can anyone tell me why these are the limits and how to get to polar limits from cartesian?
What i mean is, what is the 'a' all about? i can't find anything about it on the net, i only managed to do this question from a guess as it looked very similar to an example question in my notes but without the 'a'.
[tex]\int^{a}_{-a}\int^{\sqrt{{a^2}-{x^2}}}_{-\sqrt{{a^2}-{x^2}}}dydx[/tex] => [tex]\int^{2\pi}_{0}\int^{a}_{0}rdrd\theta=\int^{2\pi}_{0}\left[\frac{r^2}{2}\right]^{a}_{0}d\theta[/tex]
[tex]=\int^{2\pi}_{0}\frac{a^2}{2}d\theta=\left[frac{{a^2}\theta}{2}\right]^{2\pi}_{0}={\pi{a^2}}[/tex]