Parabola is the locus of the points in the plane that are equidistant from a fixed point and a fixed line.
F - fixed point: focus of the parabola
r - fixed line: directrix of the parabola
A - vertex of the parabola
d(A,F)=p/2 - focal length
r1, r2 - radial vectors of the point T
Created by Helena Halas, translated by Helena Halas and Iva Kodrnja - 3DGeomTeh - Developing project of the University of Zagreb