SSC Sample Paper Mock Test-1 SSC CGL Tear-II Paper-1

  • question_answer
    If \[\sin x+\sin y=a\] and \[\cos x+\cos y=b,\] then \[\tan \frac{x+y}{2}\]is.

    A)  \[\frac{4}{{{a}^{2}}+{{b}^{2}}}\]              

    B)  \[\frac{b}{a}\]

    C)  \[\frac{a}{b}\] 

    D)  \[\frac{4}{{{a}^{2}}-{{b}^{2}}}\]

    Correct Answer: C

    Solution :

    \[\sin x+\sin y=a\] \[\Rightarrow \]   \[2\sin \frac{x+y}{2}\cdot \cos \frac{x-y}{2}=a\] \[\cos x+\cos y=b\] i.e.        \[2\cos \frac{x+y}{2}\cdot \cos \frac{(x-y)}{2}=b\] Taking ratio, we have \[\therefore \]\[\frac{2\sin \frac{x+y}{2}\cdot \cos \frac{x-y}{2}}{2\cos \frac{x+y}{2}\cdot \cos \frac{(x-y)}{2}}=\frac{a}{b}\]\[\Rightarrow \]\[\tan \frac{x+y}{2}=\frac{a}{b}\]


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