A and B are two vectors in the xy plane that makeangles a
Chapter 7, Problem 7.30(choose chapter or problem)
A and B are two vectors in the xy plane that makeangles a and /3 with the x axis respectively. Evaluate the scalarproduct of A and B and deduce the following trigonometricidentity: cos (a /3) = cos a cos /3 + sin a sin /3.
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