The curve in red is the plot of 1+2cos(theta) and the one in purple is the plot of r=1+2cos(theta). The purple is drawn from the red. Starting from positive x -ax\is, the purple curve goes from r=3 at theta = 0 and decreases until it goes to zero, then decreases further until the minimum r=-1 at theta = pi, then increases and goes back to zero, and continues increasing until reaching another maximum r=3 at theta = 2*pi.