JEE Main & Advanced Mathematics Trigonometric Identities Question Bank Self Evaluation Test - Trigonometric Function

  • question_answer
    If \[\frac{\sin (x+y)}{\sin (x-y)}=\frac{a+b}{a-b},\] then what is \[\frac{\tan x}{\tan y}\] equal to?

    A) \[\frac{b}{a}\]              

    B) \[\frac{a}{b}\]    

    C) \[ab\]                

    D) \[1\]

    Correct Answer: B

    Solution :

    \[\frac{\sin (x+y)}{\sin (x-y)}=\frac{a+b}{a-b}\] Applying componendo and dividendo, we get \[\frac{\sin (x+y)+\sin (x-y)}{\sin (x+y)-\sin (x-y)}=\frac{(a+b)+(a-b)}{(a+b)-(a-b)}\] \[\Rightarrow \,\,\frac{2\sin \,x.cosy}{2\cos x.\sin y}=\frac{2a}{2b}\Rightarrow \,\,\tan x.\cot y=\frac{a}{b}\] \[\therefore \,\,\,\frac{\tan x}{\tan y}=\frac{a}{b}\]


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