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Welcome to Feuerbach Theorem, one of the most striking theorems in triangle geometry!
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Feuerbach Theorem: Table of Content

 

 

9.

Feuerbach Point Facts
 

8.

Feuerbach Theorem, Acute Triangle illustration
 

7.

Feuerbach Theorem, Obtuse Triangle illustration
 

6.

Feuerbach Theorem, Right Triangle illustration
 

5.

Nine-Point Center, Nine-Point Circle, Euler Line.
Interactive illustration.

4.

Spieker Center

3.

Symmedian (Lemoine) Point

2.

Steiner Point
 

1.

Mittenpunkt Point
 


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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Last updated: May 25, 2008