# Parabolas from Rays

Parabolas from Rays

This Demonstration shows how to draw the half parabola that includes a given point, has directrix parallel to the axis, and has its vertex at the origin. First divide the area between the axis and the given point into strips by parallels to the axis. Then draw rays from the origin to points between the given point and the axis. The pairwise intersections of parallels and rays are points of the parabola.

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