Simson Line -- from Wolfram MathWorld

The Simson line is the line containing the feet P_1, P_2, and P_3 of the perpendiculars from an arbitrary point P on the circumcircle of a triangle to the sides or their extensions of the triangle. This line was attributed to Simson by Poncelet, but is now frequently known as the Wallace-Simson line since it does not actually appear in any work of Simson (Johnson 1929, p. 137; Coxeter and Greitzer 1967, p. 41; de Guzmán 1999). The inverse statement to that given above, namely that the

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Simson Line -- from Wolfram MathWorld

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