Posted by Ria on Monday, May 17, 2010 at 12:33am.
Let OP be any vector with direction angles theta, beta, and gama.
Explain why cos^2theta + cos^2beta + cos^2gama = 1

Calculus  drwls, Monday, May 17, 2010 at 6:03am
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)
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