Let $P$ be any point and let $OP=r$, where $O$ is the origin and let $OP$ make an angle $\theta$ with the axis, then $r$ and $\theta$ are called Polar coordinates of the point $P$, and the coordinates may be written as $(r,\theta)$.
Find the Cartesian equations of
$\cos(\theta-\alpha)$ may be expanded
Therefore the Cartesian equation of $r\cos(\theta-\alpha)=p$ is
$Note$. The perpendicular from the origin to this line is of length $p$ and makes an angle $\alpha$ with the x-axis. This form of equation of a straight line is known as the normal or perpendicular form.
Surround your text in
**bold**, to write a math equation use, for example,