1.

If `(cos (A-B))/(cos(A+B))=(8)/(3)`, then `tanA*tanB` is _____A. `(5)/(11)`B. `(7)/(13)`C. `(8)/(5)`D. `(11)/(5)`

Answer» Correct Answer - A
(i) Use componendo and dividendo theorem , i.e.,
`(a)/(b)=(a+b)/(a-b)`
(ii) Use the formula ` cos(A-B) and cos (A+B)`.
(iii) Take cross multiplication and find `tanA+ tan B`.


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