# Parabolic Envelope from Congruent Triangles

Requires a Wolfram Notebook System

Interact on desktop, mobile and cloud with the free Wolfram Player or other Wolfram Language products.

Consider a line and a point not on . Drag the orange point along . Draw a vertical line from . The perpendicular bisector of meets at a point that traces out a parabola and is tangent to the parabola. The focus and directrix of the parabola are and because is isoceles. The part of the vertical line m inside the parabola is the reflection in of the ray .

Contributed by: Harry Calkins (March 2011)

Open content licensed under CC BY-NC-SA

## Snapshots

## Details

detailSectionParagraph## Permanent Citation

"Parabolic Envelope from Congruent Triangles"

http://demonstrations.wolfram.com/ParabolicEnvelopeFromCongruentTriangles/

Wolfram Demonstrations Project

Published: March 7 2011