Feuerbach Theorem: Table of
Content




Feuerbach Points and NinePoint Circle with interactive
animation, manipulation, and stepbystep construction.


Feuerbach
Point Facts


iPad Apps: Apollonius Software. Feuerbach Point. Triangle, Incircle, Nine point circle, Tangent circles, Orthocenter, Midpoint.
Interactive Geometry Software. 

GeoGebra, Dynamic Geometry:
Internal Feuerbach Point
HTML5 Animation for Tablets (iPad, Nexus..) 

Feuerbach
Theorem, Acute Triangle
illustration


Feuerbach
Theorem,
Obtuse Triangle illustration


Feuerbach
Theorem,
Right Triangle illustration


NinePoint Center,
NinePoint Circle, Euler Line.
Interactive illustration.


Spieker Center 

Symmedian (Lemoine) Point 

Steiner Point


Mittenpunkt Point

Karl Feuerbach (18001834) was a
geometer who discovered the
ninepoint 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.

