SSC Sample Paper Mock Test-18 SSC CGL Tear-II Paper-1

  • question_answer
    If a and p are complementary angles, then what is the value of \[\sqrt{\text{cosec}\alpha \cdot \text{cosec}\beta }{{\left( \frac{\sin \alpha }{\sin \beta }+\frac{\cos \alpha }{\cos \beta } \right)}^{-\,\,\frac{1}{2}}}?\]

    A) 0

    B)  1  

    C)  2

    D)  None of these

    Correct Answer: B

    Solution :

    Given, \[\alpha +\beta =90{}^\circ \]                              ?(i)
    \[\therefore \]      \[\sqrt{(\text{cosec}\alpha \cdot \text{cosec}\beta \text{)}}{{\left( \frac{\sin \alpha }{\sin \beta }+\frac{\cos \alpha }{\cos \beta } \right)}^{1/2}}\]
    \[=\frac{1}{{{(\sin \alpha \sin \beta )}^{1/2}}}{{\left( \frac{\sin \alpha \cos \beta +\cos \alpha +\sin \beta }{\sin \beta \cos \beta } \right)}^{-1/2}}\]
    \[=\frac{1}{{{(sin\alpha sin\beta )}^{1/2}}}{{\left\{ \frac{\sin (\alpha +\beta )}{\sin \beta \cos \beta } \right\}}^{-1/2}}\]
    \[=\frac{1}{{{(\sin \alpha \sin \beta )}^{1/2}}}{{\left\{ \frac{\sin 90{}^\circ }{\cos (90-\alpha )\sin \beta } \right\}}^{-1/2}}\]
    [from Eq. (i)]
    \[=\frac{1}{{{(\sin \alpha \sin \beta )}^{1/2}}}\times (\sin \alpha \sin \beta )1/2=1\]


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