Welcome to Triangles, Theorems and Problems

Geometry, Machu Picchu

Congruence

Congruence. Index.

Similarity

Similarity, Proportions. Index.
 

Areas
Areas Index.

Equilateral triangle
Equilateral Triangle

Isosceles triangle

Isosceles Triangle

Right Triangle

Right Triangle Index.

Obtuse Triangle Index
Obtuse Triangle Index.

Median of a triangle, Index

Median Index.
Theorems and Problems.
 

Altitude of a triangle

Altitude Index.
Theorems and Problems.
 

Special Right Triangle 30-60 Index

Special Right Triangle 30-60 Index.

Special right triangle 30 60
Special Right Triangles Index.

Triangles and Squares
Triangle and Squares.
 

Area of a triangle, Index
Area of a Triangle.Index

Euclid's Elements 23 definitions

Euclid's Elements Book I, 23 Definitions.

Centers
Triangle Centers Index.

Triangle Incenter
Incenter.Index
 

Excenter

Excenter Index

Centroid

Centroid Index.

Circumcenter
Circumcenter Index.

Triangle Orthocenter
Orthocenter.
 

Napoleon Theorem

Napoleon Theorem

Triangle Area

Triangle Area Problem.

Equilateral triangle
Equilateral triangle.

Triangle Orthocenter
Problem 132.Triangle, 60 degree, Orthocenter,

Van Aubel cevians

Problem 125. Area of Triangle, Star, Trisection of Sides

Cevian Ratio

Problem 129. Triangle, Concurrent Cevians, Sum of Ratios.

Centroid, Incenter
Problem 127. Centroid and Incenter of a Triangle, Parallel, Proportions.

Triangle Incenter
Problem 126. Incenter of Triangle, Angle Bisector, Proportions.

 

Elearning 125

Problem 125. Area of Triangle, Star, Trisection of Sides

Elearning 124

Problem 124. Area of triangle, Similarity, Trisection of Sides

Elearning 123
Problem 123. Area of triangle, Similarity, Trisection of Sides

Marion Walter Theorem
Problem 122. Marion Walter's Theorem

Problem 120: Geometry Elearning

Problem 120. Area of triangle, incenter, excircles

Problem 119. Geometry Elearning

Problem 119. Area of triangle, incenter, excircle

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

Problem 115
Problem 115. Area of triangle, excircles

 

Math Problem

Intouch and Extouch Triangles, Areas

Math Problem

Contact Triangles Areas, Incircle, Excircle

Math Problem
Contact Triangles Areas, Incircle, Excircle, Inradius, Exradius

Math Problem
Area of the Contact Triangle, inradius, circumradius

Morley: dynamic geometry

 

Feuerbach points

 

Marion Walter theorem

Taylor circle theorem
 

 

Triangle similarity problem

 

Jacobi Isogonic theorem

 

Schiffler point

Van Aubel theorem
 

 

Triangle: Incircle, excircles

 

Feuerbach points

 

Newton Gauss line

triangle incircles
 

 

 

 



 

 

 

 



 

 

 

 


Mascheroni Construction with compass alone.


 

 

 

 


 


 
 

Right Triangles, Formulas and Facts

Mind Map of the Pythagorean Theorem
Proofs by shears, translation, similarity. Facts.


 


Triangle and Squares 20

 

  

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