1.

If tan(A +B) = And tan(A -B) = y, find the values of tan 2A And tan 2B.

Answer»

Given tan(A +B) = x And tan(A –B) = y 

Consider tan 2A = tan(A +A) 

= tan(A +B +A –B) 

We know that tan(A+B) = \(\frac{tanA+tanB}{1-tanAtanB}\)

⇒ tan(A + B + A - B) = \(\frac{tan(A+B)+tan(A-B)}{1-tan(A+B)tan(A-B)}\)

\(\frac{x+y}{1-xy}\)

Consider tan 2B = tan(B +B) 

= tan(B +A +B –A)

\(\frac{tan(B+A)+tan(B-A)}{1-tan(B+A)tan(B-A)}\)

We know that tan(-θ) = - tan θ

\(\frac{tan(A+B)-tan(A-B)}{1+tan(A+B)tan(A-B)}\)

\(\frac{x-y}{1+xy}\)



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