9. Polar Equations

Given the polar equation $r=7\cos \left(\theta \right)$, which of the following is the corresponding Cartesian equation?

Given the point with polar coordinates $(3,\frac{\pi }{4})$, which of the following polar coordinate pairs labels the same point?

Which of the following is a polar equation for the curve represented by the Cartesian equation $x^2+y^2=3$?