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

Triangle -- from Wolfram MathWorld

Anticevian Triangle -- from Wolfram MathWorld

Fuhrmann Triangle -- from Wolfram MathWorld

Half-Altitude Triangle -- from Wolfram MathWorld

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Outer Vecten Triangle -- from Wolfram MathWorld

Outer Inscribed Squares Triangle -- from Wolfram MathWorld

code golf - Draw A Reuleaux Triangle! - Code Golf Stack Exchange

BCI Triangle -- from Wolfram MathWorld

D-Triangle -- from Wolfram MathWorld

Taylor Center -- from Wolfram MathWorld

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Extangents Triangle -- from Wolfram MathWorld

Triangle Area -- from Wolfram MathWorld

Snark -- from Wolfram MathWorld