(Addition law) Obtain cos (a - (3) = cos a cos {3 + sin a
Chapter 9, Problem 9.2(choose chapter or problem)
(Addition law) Obtain cos (a - (3) = cos a cos {3 + sin a sin {3 by using a = [cos a, sin a]. b = [cos {3, sin {3]. where o ~ a ~ (3 = 27f.
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