Given that tanA=sinA/cosA and tanB=sinB/cosB. Find tan(A+B)

Answer 1

The identity for tan(A+B) = (tan A + tan B)/(1 - tan A tan B)

In order to derive this formula you need the identity for sin(A+B) and cos(A+B) and the trick is to divide the numerator and denominator by cos A cos B.