Given a triangle ABC and a point D on its circumcircle, then the feet H,F,E of the perpendiculars drawn from D to the sides (or their extensions) are collinear. The line HFE is called the Simson line of D.

Robert Simson (1687 - 1768) was a Scottish mathematician and professor of mathematics at the University of Glasgow.

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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

Circle

Perpendicular lines

Collinear Points

Cyclic Quadrilateral

Simson line

Classical Theorems

Dynamic Geometry

GeoGebra

HTML5 and Dynamic Geometry

iPad Apps

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