Polar coordinates
problem
Maltese cross
Sketch the graph of $xy(x^2 - y^2) = x^2 + y^2$ consisting of four curves and a single point at the origin. Convert to polar form. Describe the symmetries of the graph.
problem
Polar flower
This polar equation is a quadratic. Plot the graph given by each
factor to draw the flower.
article
An introduction to polar coordinates
This introduction to polar coordinates describes what is an effective way to specify position. This article explains how to convert between polar and cartesian coordinates and also encourages the creation of some attractive curves from some relatively easy equations.