Replace the Cartesian equation with equivalent polar equations. x=7

The given Cartesian equation is $x=7$
${\displaystyle x=r\cos \theta ,y=r\sin \theta }$
To replace Cartesian equation with equivalent polar equations as follows,
Cartesian equation $=x=7$.
Equivalent polar equation ${\displaystyle =x=r\cos \theta }$
Substituting $x=7$,${\displaystyle x=r\cos \theta }$
Therefore, the equivalent polar equation is ${\displaystyle r\cos \theta =7}$