Wolfram Demonstrations Projecthttp://demonstrations.wolfram.com/An Open Resource of Interactive Mathematica VisualizationsCopyright 2009 Wolfram Demonstrations Project & ContributorsLimaçons as Envelopes of Circleshttp://demonstrations.wolfram.com/LimaconsAsEnvelopesOfCircles/]]>http://demonstrations.wolfram.com/LimaconsAsEnvelopesOfCircles/