# Cartesian to polar

• Nov 20th 2011, 12:48 PM
nerdo
Cartesian to polar
Hi

I just have a quick question: how do I change x=1-y in to polar coordinates.

It is for an integration limit problem that I am working on.

Thanks

Nerdo
• Nov 20th 2011, 12:53 PM
Quacky
Re: Cartesian to polar
Is there something stopping you from substituting in $\displaystyle x=r\cos\theta$ and $\displaystyle y=r\sin\theta$? Am I missing something?
• Nov 20th 2011, 12:57 PM
nerdo
Re: Cartesian to polar
Quote:

Originally Posted by Quacky
Is there something stopping you from substituting in $\displaystyle x=r\cos\theta$ and $\displaystyle y=r\sin\theta$? Am I missing something?

once I done that I get $\displaystyle cos\theta+sin\theta=1/r$

Is it possible to write it in terms of theta
• Nov 20th 2011, 01:07 PM
Quacky
Re: Cartesian to polar
It is possible, I think.

$\displaystyle \cos\theta{+}\sin\theta =\frac{1}{r}$

Squaring both sides gives:

$\displaystyle (\cos\theta{+}\sin\theta )^2=\frac{1}{r^2}$

$\displaystyle 1+\underbrace{2\sin\theta\cos\theta}=\frac{1}{r^2}$
Recognize this, at all? (Wink)

Edit: Corrected a mistake.
• Nov 20th 2011, 01:09 PM
Quacky
Re: Cartesian to polar
I've just editted a mistake from the post above.