Geometry: Nagel Points, Theorems and Problems - Table of Content

Nagel Point Theorem.
Concurrency. Interactive proof with Flash animation proof. 

Puzzle of the Nagel Point: 22 pieces of polygons.

Nagel Point Theorem - Flowchart Proof .
 

Geometry Problem 1455.
Nagel Point, Excircles, Incircle, Congruent Segments, iPad. Step-by-step illustration using GeoGebra.

Geometry Problem 689.
Triangle, Three Excircles, Tangency points, Tangent lines, Concurrent Lines, Mind Map.

Geometry Problem 687.
Triangle, Three Excircles, Tangency points, Concurrent Lines.

Geometry Problem 684: Outer Nagel Point.
Triangle, Excircles, Incircle Tangency points, Concurrent lines, Semi-perimeter, Ceva theorem.

Geometry Problem 683: Nagel Point.
Triangle, Excircles, Tangency points, Concurrent lines, Semi-perimeter, Ceva theorem.

Geometry Problem 138. Nagel's Theorem, Orthic Triangle, Altitudes, Circumradius, Perpendicular.

Gergonne Point Theorem. Concurrency. Interactive proof with animation.

Key concept: Ceva's Theorem.

Semiperimeter and excircles of a triangle.

Semiperimeter and incircle of a triangle.

Semiperimeter, incircle and excircles of a triangle.