C.a.R. > Applications > Conic Sections > Parabola with Focus

The track of all points with equal distance to a given point and a line is a parabola. You can move the point and the point on the line. Move with the right mouse button to snap to grid points. Note that the green angles are equal. This is, why the point is called the focal point.

Technical Information

The parabola is a track here. The function expression is a bit tricky, since we want to avoid x--1 and get x+1 instead. Moreover, the green angles you see are different on the right and on the left. They are hidden, if they become larger than 90 using conditional formatting.