Tangents to the circumcircle of triangle ABC, at points A, B, and C, meet sides BC, AC, and BA at points E, F, and D, respectively. Then E, F, D are collinear and line DEF is called the Lemoine line of triangle ABC.

Interactive step-by-step animation using GeoGebra

This step-by-step interactive illustration was created with GeoGebra.

- To explore (show / hide): click/tap a check box.
- To stop/play the animation: click/tap the icon in the lower left corner.
- To go to first step: click/tap the "Go to step 1" button.
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GeoGebra is free and multi-platform dynamic mathematics software for all levels of education that joins geometry, algebra, tables, graphing, statistics and calculus application, intended for teachers and students. Many parts of GeoGebra have been ported to HTML5.

Geometry Problems

Open Problems

Visual Index

Ten problems: 1411-1420

All Problems

Triangle

Circumcircle

Circles

Circle Tangent Line

Classical Theorems

Dynamic Geometry

Collinear Points

GeoGebra

HTML5 and Dynamic Geometry

iPad Apps

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