# Finding a Cartesian equation for an r value

• September 8th 2013, 04:34 PM
Finding a Cartesian equation for an r value
How would I find a Cartesian equation for r = 4secx?

Thanks.
• September 8th 2013, 06:15 PM
Soroban
Re: Finding a Cartesian equation for an r value
$\text{How would I find a Cartesian equation for: }\: r \,=\, 4\sec\theta\,?$
We have: . $r \:=\:\frac{4}{\cos\theta} \quad\Rightarrow\quad r\cos\theta \:=\:4 \quad\Rightarrow\quad x \,=\,4$