Graphing in polar coordinates is still a bit clunky in GeoGebra 4, so this sketch does a bit of the clunky work for the student by parameterizing the polar equation. Enter the function of the radius in terms of theta as r(t), and then manually progress t or press play to see the graph. See the many types of polar curves to explore at Wolfram Mathworld: http://bit.ly/rzsnMe (shortened) or http://mathworld.wolfram.com/topics/PolarCurves.html
Find more sketches at mathhombre.blogspot.com