# trig

A and B are positive acute angles. if sin A=4/5 and cos B=8/17 find the value of tan (A-B)

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1. cosA = 3/5
sinB = 15/17

tanA = 4/3
tanB = 15/8

tan(A-B) = (tanA-tanB)/(1+tanAtanB)
= (4/3 - 15/8)/(1+(4/3)(15/8))
= (-13/24)/(7/2)
= -13/84

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2. thanks

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