Convert Cartesian function to polar function

Question

A problem on my math homework is $x = -4$ convert to a polar function. What are the steps, the examples in my book are only for $y=x$ functions.

Answer 1

To convert Cartesian to polar, remember that we use $x= r\cos \theta$ and $y = r \sin \theta$. Since we know $x=-4$, just replace $x$ by $-4$ to get $\color{red}{r\cos\theta = -4}$