External Path Length -- from Wolfram MathWorld

The sum over all external (square) nodes of the lengths of the paths from the root of an extended binary tree to each node. For example, in the tree above, the external path length is 25 (Knuth 1997, pp. 399-400). The internal and external path lengths are related by E=I+2n, where n is the number of internal nodes.

Great circle - Wikipedia

Huffman Coding -- from Wolfram MathWorld

Cross Product -- from Wolfram MathWorld

Equal Parallelians Point -- from Wolfram MathWorld

Angle Bisector -- from Wolfram MathWorld

Graph Path -- from Wolfram MathWorld

Graph Path -- from Wolfram MathWorld

Wolfram Alpha: The Physicist Turned a Successful Entrepreneur - FourWeekMBA

upload.wikimedia.org/wikipedia/commons/8/86/Logari

Tutte Polynomial -- from Wolfram MathWorld

Huffman Coding -- from Wolfram MathWorld