Use the half-angle identity tan A 2 = sin A 1 + cos A to derive the equivalent identity
Chapter 5, Problem 53(choose chapter or problem)
Use the half-angle identity tan A 2 = sin A 1 + cos A to derive the equivalent identity tan A 2 = 1 - cos A sin A by multiplying both the numerator and the denominator by 1 - cos A.
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