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Feuerbach Theorem: Table of
Content
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Feuerbach Points and Nine-Point Circle with interactive
animation, manipulation, and step-by-step construction.
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Feuerbach
Point Facts
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iPad Apps: Apollonius Software. Feuerbach Point. Triangle, Incircle, Nine point circle, Tangent circles, Orthocenter, Midpoint.
Interactive Geometry Software. |
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GeoGebra, Dynamic Geometry:
Internal Feuerbach Point
HTML5 Animation for Tablets (iPad, Nexus..) |
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Feuerbach
Theorem, Acute Triangle
illustration
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Feuerbach
Theorem,
Obtuse Triangle illustration
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Feuerbach
Theorem,
Right Triangle illustration
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Nine-Point Center,
Nine-Point Circle, Euler Line.
Interactive illustration.
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Spieker Center |
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Symmedian (Lemoine) Point |
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Steiner Point
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Mittenpunkt Point
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Karl Feuerbach (1800-1834) was a
geometer who discovered the
nine-point circle of a triangle.
One of the most striking theorems in
triangle geometry is
Feuerbach's theorem. He wrote in his 1822
paper:
The circle which passes through the feet of the altitudes of a
triangle touches all four of the circles which are tangent to
the three sides of the triangle; it is internally tangent to the
inscribed circle and externally tangent to each of the circles
which touch the sides of the triangle externally.
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