Wolfram Demonstrations Projecthttp://demonstrations.wolfram.com/An Open Resource of Interactive Mathematica VisualizationsCopyright 2009 Wolfram Demonstrations Project & ContributorsFocus and Directrix in a Quadratic Bézier Curvehttp://demonstrations.wolfram.com/FocusAndDirectrixInAQuadraticBezierCurve/]]>http://demonstrations.wolfram.com/FocusAndDirectrixInAQuadraticBezierCurve/Rational Cubic Bézier Curveshttp://demonstrations.wolfram.com/RationalCubicBezierCurves/]]>http://demonstrations.wolfram.com/RationalCubicBezierCurves/