Posted by Ria on .
Let OP be any vector with direction angles theta, beta, and gama.
Explain why cos^2theta + cos^2beta + cos^2gama = 1

Calculus 
drwls,
The Pythagorean therem, applied twice, says that the sum of the squares of projections onto three perpendicular axes, of a segment of any vector with length 1, equals the length of the vector (1)