The first thing you should know in this case is that the equation is written in a rectangular form.
It can be written in polar form.
To do this, you must make the following change of variables:
x = r * cos (theta)
We have then:
r * cos (theta) = 5
r = 5 / cos (theta)
r = 5 * sec (theta)
Answer:
The polar form is:
r = 5 * sec (theta)
Note: the equation was already written in rectangular form.