Wolfram Demonstrations Projecthttp://demonstrations.wolfram.com/An Open Resource of Interactive Mathematica VisualizationsCopyright 2009 Wolfram Demonstrations Project & ContributorsStandard Form of the Equation of a Circlehttp://demonstrations.wolfram.com/StandardFormOfTheEquationOfACircle/]]>http://demonstrations.wolfram.com/StandardFormOfTheEquationOfACircle/