Excenter of a triangle - Table of Content

Triangle Centers.

Proposed Problem 419.
Triangle, Cevian, Incircle, Excircle, Inradius, Exradius

Proposed Problem 380.
Triangle, Excenter, Parallel to a side, Angle, Congruence.

Proposed Problem 379.
Triangle, Excenter, Parallel to a side, Angle, Congruence.

Proposed Problem 376.
Triangle, Excenter, Internal and External Angle Bisectors.

Proposed Problem 375.
Triangle, Excenter, External Angle Bisectors.

Proposed Problem 320.
Triangle, Circumcircle, Incenter, Excenter, Collinear points.

Proposed Problem 294.
Right triangle, Circumcenter, Excenter, Hypotenuse, Perpendicular.

Second Ajima-Malfatti Point
Interactive illustration.
Excenters of a triangle

Feuerbach Points and Nine-Point Circle with interactive animation, manipulation, and step-by-step construction.
Incenter, Incircle, Excenters, Excircles.

Incenter, Excenter, Incircle, Excircle Using TracenPoche Dynamic Software
Step-by-Step construction, Manipulation, and animation.

Heron's Formula.
Key facts and a purely geometric step-by-step proof.
Incenter, Incircle, Excenter.
 

Semiperimeter, incircle and excircles of a triangle.

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

Right Triangles, Formulas and Facts
Pythagorean theorem, Similarity, Geometric mean, hypotenuse, legs, semiperimeter, altitude, median, similar shapes areas, centers, orthocenter, incenter, incircle, centroid, circumcenter, radius, inradius, excenters, exradius.

Feuerbach Theorem, Acute Triangle illustration
 

Feuerbach Theorem, Obtuse Triangle illustration
 

Feuerbach Theorem, Right Triangle illustration
 

Proposed Problem 207. Right Triangle, Hypotenuse, Incenter, Inradius, Excenter, Exradius relative to the hypotenuse.  

Proposed Problem 206. Area of a Right Triangle, Inradius, and Excenter, Exradius relative to the hypotenuse.  

Proposed Problem 204. Right Triangle, Incircle, Excenters, Excircles, Inradius, Exradii.  

Proposed Problem 202. Right Triangle, Incircle, Excenters, Excircles relatives to catheti, Points of Tangency, Exradius, Semiperimeter.  

Proposed Problem 200. Right Triangle, Incircle, Excircles, Points of Tangency, Inradius.

Proposed Problem 197. Area of a Triangle, Side, Incircle, Inradius, Excenter, and Exradius.

Proposed Problem 196. Triangle, Incircle, Inradius and Exradii Formula.

Journey to the Center of a Triangle (1976). Incenter, Circumcenter, Centroid, Orthocenter.

Proposed Problem 195. Area of a Triangle, Incircle, Inradius, Excenters, Exradii.  

Proposed Problem 159. Distances from the Circumcenter to the Incenter and the Excenters.  

Proposed Problem 158. Relation between the Circumradius, Incircle, Inradius and Exradii of a triangle.  

Proposed Problem 120. Area of triangle, incenter, excircles, tangent.

Proposed Problem 119. Area of triangle, incenter, excircle, tangent.

Proposed Problem 118. Area of triangle, incenter, excenter, tangent.

Proposed Problem 117. Area of triangle, incenter, excircles, tangent.

Proposed Problem 114. Area of triangle, incenter, incircle, excircle.

Proposed Problem 113. Area of triangle, incenter, incircle, excircle.

Intouch and Extouch Triangles. Puzzle cut: 20 Piece Classic
Based on Proposed Problem 86.

Proposed Problem 86. Intouch and Extouch Triangles, Excircles, Areas.

Contact Triangles. Puzzle cut: 22 Piece Polygons
Based on Proposed Problem 85. Excircles

Proposed Problem 85. Contact Triangles Areas, Incircle, Excircles.

Proposed Problem 84. Contact Triangles Areas, Incircle, Excenter, Excircle, Inradius, Exradius.

Proposed Problem 40.
Triangle, Incenter, Excenter, Angles 80, 40, Distances.

Geometry Online Glossary .
Geometry Glossary based on the new New York State mathematics standards initiative. Incenter, Incircle.

Euclid's Elements Book I, 23 Definitions. One-page visual illustration.
Euclid's Elements Book. Index