## Thomas' Calculus 13th Edition

Polar equation: $r^2 \sin^2 \theta=4r \cos \theta$ or, $r^2=\dfrac{4\cos \theta}{\sin^2 \theta}$
The conversion of polar coordinates and Cartesian coordinates are described as follows: 1. $r^2=x^2+y^2$ and $r=\sqrt {x^2+y^2}$ 2. $\tan \theta =\dfrac{y}{x} \implies \theta =\tan^{-1} (\dfrac{y}{x})$ 3. $x=r \cos \theta$ and 4. $y=r \sin \theta$ Now, we have the equivalent Polar equation: $r^2 \sin^2 \theta=4r \cos \theta$ or, $r^2=\dfrac{4\cos \theta}{\sin^2 \theta}$