If A + B = 45∘, find tanA + tanB
1 - tanAtanB
We have A+B = 45∘ and we have to find tanA+tanB. In the options we have tanAtanB also. At this point, we should be able to guess that we are going to use tan (A+B)
Tan (A+B) = tan45 = 1 = tanA+tanB1−tanA+tanB
⇒ tanA + tanB = 1 - tanAtanB
Key steps/concepts: (1) Expansion of tan(A+B)
(2) Guessing that the terms in options and question are related to tan (A+B).