Triangles: Theorems and Problems 40




Triangle with the bisectors of the
exterior angles. Collinearity. Key concept:
Menelaus Theorem.


Napoleon's Theorem.
A purely geometric proof. It uses the Fermat point to prove Napoleon
without transformations.
Escalene and Equilateral triangles. 

The Bevan Point The
circumcenter of the excentral triangle. Illustration with animation.


The Bevan Point:
Puzzle 

Angle between two
Simson Lines. Proof with animation.


Simson Line. A proof
of Simson line with animation. 

Butterfly Theorem
Proof with animation. 

Butterfly Theorem: Puzzle. 

Langley's
Problem Adventitious
angles. 20° isosceles triangle with animation.


Triangle with Squares Problem
