r = Φ13 will be a spiral when graphed on a polar axis.
It is flipped left to right over the vertical axis when you add a negative sign in front.
r = - Φ13
You can graph these two on Desmos.com using the Polar Limacon graph option.
I could not paste a screenshot of my graph here due to Wyzant's character limit on this answer.
However, your question asks about graphing on the Cartesian plane.
Technically, the polar axes that I used here are not called the Cartesian plane.
If you need to have it on the Cartesian plane, that will complicate things a bit.
Check to be sure that the question requires the Cartesian plane.