Triangle -- from Wolfram MathWorld

A triangle is a 3-sided polygon sometimes (but not very commonly) called the trigon. Every triangle has three sides and three angles, some of which may be the same. The sides of a triangle are given special names in the case of a right triangle, with the side opposite the right angle being termed the hypotenuse and the other two sides being known as the legs. All triangles are convex and bicentric. That portion of the plane enclosed by the triangle is called the triangle interior, while the

Magog Triangle -- from Wolfram MathWorld

Pascal's Triangle -- from Wolfram MathWorld

Spherical Triangle -- from Wolfram MathWorld

linear programming solver –

How to Calculate the Sides and Angles of Triangles Using

Hexyl Circle -- from Wolfram MathWorld

Euler Triangle -- from Wolfram MathWorld

Orthic Triangle -- from Wolfram MathWorld

How to Calculate the Sides and Angles of Triangles Using

Lemoine Triangle -- from Wolfram MathWorld