# Math Help - Converting a polar equation to Cartesian form.

1. ## Converting a polar equation to Cartesian form.

I have been thinking about since morning, but didn't seen to find a way to even start to solve this:

Get the cartesian equation for the curve r=2*cos a , and make the graph of this curve

Can anyone help me? Thank you! (:

2. ## Re: Circumference

Originally Posted by weber
I have been thinking about since morning, but didn't seen to find a way to even start to solve this:

Get the cartesian equation for the curve r=2*cos a , and make the graph of this curve

Can anyone help me? Thank you! (:
assuming you mean ...

$r = 2\cos{\theta}$ (instead of "a")

note that $x = r\cos{\theta}$ is one of your basic conversion equations.

rearranging ... $\frac{x}{r} = \cos{\theta}$

substitute $\frac{x}{r}$ for $\cos{\theta}$ in your original equation ...

$r = 2 \cdot \frac{x}{r}$

$r^2 = 2x$

also note that $r^2 = x^2+y^2$ ...

$x^2 + y^2 = 2x$

... and this would be the equation of what conic section?

Moderator edit: Excellent reply restored. Post #3 deleted.