# Thread: Finding a Cartesian equation for an r value

1. ## Finding a Cartesian equation for an r value

How would I find a Cartesian equation for r = 4secx?

Thanks.

2. ## Re: Finding a Cartesian equation for an r value

Hello, Shadow236!

$\text{How would I find a Cartesian equation for: }\: r \,=\, 4\sec\theta\,?$

I will assume you know the conversion identities.

We have: . $r \:=\:\frac{4}{\cos\theta} \quad\Rightarrow\quad r\cos\theta \:=\:4 \quad\Rightarrow\quad x \,=\,4$

3. ## Re: Finding a Cartesian equation for an r value

This makes sense. Thank you!