Decide on a set of values, say,

rad

Then calculate the r value for each . They are

(respectively)

What do you do with negative r values? Well, you make the r value positive and then add (or subtract) rad to the angle.

So we wish to plot the set of points:

<--

Then you plot the points on polar coordinate graph paper and sketch in a smooth curve between the points. I get the graph below.

-Dan