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

\(\displaystyle{x}={r}{\cos{\theta}},{y}={r}{\sin{\theta}}\)

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