Triangle -- from Wolfram MathWorld

Regular Tetrahedron with a square inside it -- from Wolfram MathWorld

Bell Triangle -- from Wolfram MathWorld

The Wolfram MathWorld List of Unsolved Problems

SteinerCircumellipse Wolfram Function Repository

Altitude -- from Wolfram MathWorld

The Yanghui Triangle, Part I – The Shaw Show

Using Wolfram, Alpha to Understand Mathematics

Paralogic Triangles -- from Wolfram MathWorld

Exmedian Point -- from Wolfram MathWorld

Penrose Tiles -- from Wolfram MathWorld

Pin by Dangthanhvan on Shaping Graphing, Cymatics, Triangular prism

Third Brocard Triangle -- from Wolfram MathWorld