Online Geometry: Equilateral Triangles, Theorems and Problems  Page 1




Euclid's Elements
Book I, 23 Definitions. Onepage visual illustration.
Equilateral triangle. 

Euclid's Elements Book I, Proposition 3: Given two unequal straight
lines, to cut off from the greater a straight line equal to the less.
Equilateral triangle. 

Euclid's Elements Book I, Proposition 2: To place at a given point (as
an extremity) a straight line equal to a given straight line.
Equilateral triangle. 

Euclid's Elements Book I, Proposition 1: On a given finite line to
construct an equilateral triangle 

Euclid's
Elements, Book XIII, Proposition 10 One page visual illustration. 

Napoleon's
theorems and problems, Index.
Equilateral triangle. 

Geometry Problem 404.
External Equilateral triangles, Congruent and Concurrent Lines. 

Da Vinci Tetrahedron and Jenn 3D tool for visualizing
Coxeter polytopes.
Jenn 3D is a free software license program for visualizing
regular polytopes in stereographic projection. 

Da Vinci Octahedron and Jenn 3D tool for visualizing Coxeter
polytopes.
Jenn 3D is a free software license program for visualizing
regular polytopes in stereographic projection. 

Da Vinci Icosahedron and Jenn 3D tool for visualizing
Coxeter polytopes.
Jenn 3D is a free software license program for visualizing
regular polytopes in stereographic projection. 

Optical Prism with Equilateral Triangle Form.
Scene created using Prism HD for iPad. 

Second Fermat Point: Static diagram.
Second Fermat Point: Dynamic diagram.
Triangle, Equilateral triangles, Concurrent lines, GeoGebra, HTML5 Animation for Tablets (iPad, Nexus) 

Lester Circle Theorem.
Equilateral Triangle. 

Geometry Problem 1323.
Square, Angle Trisector, Diagonal, Regular Dodecagon, Area, 3060 degrees. 

Geometry Problem 1319.
Hexagons, Equilateral Triangles, Center, Midpoints. 

Geometry Problem 1318.
Rectangle, Equilateral Triangle, Distances, Perpendicular, Measurement. 

Geometry Problem 1314.
Equilateral Triangle, Incircle, Inscribed Circle, Tangent, Congruence. 

Geometry Problem 1313.
Regular Decagon, Pentadecagon, Equilateral Triangle, Congruence. 

Geometry Problem 1284.
Two Equilateral Triangle, Midpoint, Congruence. 

Geometry Problem 1283.
Two Equilateral Triangle, Perpendicular, Midpoint. 

Geometry Problem 1277.
Equilateral Triangle, Circumcircle, Externally Tangent Circles, Tangent Line, Measurement. 

Geometry Problem 1276.
Equilateral Triangle, Circumcircle, Internally Tangent Circles, Tangent Line, Measurement. 

Geometry Problem 1275.
Equilateral Triangle, Perpendicular, Projection, Metric Relations, Measurement. 

Geometry Problem 1238
Square, Equilateral Triangle, Metric Relations. Mobile Apps. 

Geometry Problem 1234
Quadrilateral, 60 Degrees, Midpoint, Congruence, Cyclic Quadrilateral, Concyclic Points. 

Geometry Problem 1230
Quadrilateral, 60 Degrees, Congruence, Metric Relations. 

Geometry Problem 1225
Equilateral Triangle, Circumcircle, Angle Bisector, Congruence. 

Geometry Problem 1220
Equilateral Triangles, Midpoints, 60 Degrees, Congruence. 

Geometry Problem 1219
Equilateral Triangles, Midpoints, 60 Degrees, Congruence, Rhombus. 

Geometry Problem 1218
Triangle, Equilateral Triangles, Midpoints. 

Geometry Problem 1212
Equilateral Triangle, Equilateral Hexagon, Concurrent Lines. 

Geometry Problem 1205
Triangle, Centroid, Outer and Inner Napoleon Equilateral Triangles. 

Geometry Problem 1199
Equilateral Triangle, Square, Altitude, Circle, Incircle, Inradius, Metric Relations. 

Geometry Problem 1194
Equilateral Triangle, Perpendicular, Distance, Side, Metric Relations. 

Geometry Problem 1161.
Scalene Triangle, 60 Degrees, Angle, Orthocenter, Circumcenter, Equilateral Triangle, Congruence. 

Geometry Problem 1147.
Scalene Triangle, Orthocenter, Circumcenter, Congruence, Equilateral Triangle. 

Geometry Problem 1126.
Equilateral Triangle, Circumcircle, Metric Relation, Harmonic Mean. 

Geometry Problem 1125.
Triangle, Four Equilateral Triangles, Centroid, Midpoint. 

Geometry Problem
1120.
Isosceles Right Triangle, 120 Degree, Angle, Equilateral, Metric Relations. 

Geometry Problem
1115.
Right Triangle, Angle Trisection, Equilateral Triangle. 

Geometry Problem
1092.
Equilateral Triangle, Square, Circle, Tangent, 90 Degree, Sangaku. 