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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Ten problems: 1411-1420
HTML5 and Dynamic Geometry
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