Compute tan(x + y) and tan(x - y)

Given tanx = 1/2 and tany = 1/3, compute tan(x + y) and tan(x - y).

tan(x+y) = (tanx + tany)/(1- tanx tany) = (1/2 + 1/3)/(1 - 1/6) = 1

tan(x-y) = (tanx - tany)/(1+ tanx tany) = (1/2 - 1/3)/(1 + 1/6) = 1/7

It is that simple once you got it.

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