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 \(\displaystyle{r}{\cos{\theta}}={7}\)