Napoleon Triangles
The inner Napoleon triangle is the Triangle 
formed by the centers of internally erectedEquilateral Triangles 
, 
, and 
on the sidesof a given Triangle 
. It is an Equilateral Triangle.
The outer Napoleon triangle is the Triangle 
formed by the centers of externally erectedEquilateral Triangles 
, 
, and 
on thesides of a given Triangle . It is also an Equilateral Triangle.
References
Coxeter, H. S. M. and Greitzer, S. L. Geometry Revisited. Washington, DC: Math. Assoc. Amer., pp. 60-65, 1967.
- Erdös-Selfridge Function
- Erdös Squarefree Conjecture
- Erdös-Szekeres Theorem
- Erf
- Erfc
- Erfi
- Ergodic Measure
- Ergodic Theory
- Ergodic Transformation
- Erlanger Program
- Ermakoff's Test
- Error
- Error-Correcting Code
- Error Curve
- Error Function
- Error Function Distribution
- Error Propagation
- Escher's Map
- Escribed Circle
- Essential Singularity
- Estimate
- Estimator
- Eta Function
- Et-Function
- Ethiopian Multiplication