Quadratic curve is also called conic section obtained as the intersection of a cone (more precisely, a right circular conical surface) with a plane. Conic sections are exactly those curves that, for a point F (in black), a line L (also in black) not containing F and a non-negative number e, are the locus of points whose distance to F equals e times their distance to L. F is called the focus, L the directrix, and e the eccentricity. Drag the pivot (the blue one) and see more features.

It is a parabola when e equals 1, ellipse when e is less than 1 and hyperbola when e is more than 1.

© Yang HJ 2013.