SSC Sample Paper Mock Test-5 SSC CGL Tear-II Paper-1

  • question_answer
    If \[\cos \,\,(\alpha +\beta )=\frac{4}{5}\] and \[\sin \,\,\left( \alpha -\beta  \right)=\frac{5}{13},\alpha ,\beta \] lies between 0 and \[\frac{\pi }{4},\] then die value of \[\tan 2\alpha \]

    A)  \[\frac{56}{33}\]          

    B)  \[\frac{56}{23}\]

    C)  \[\frac{43}{33}\]                                  

    D)  \[\frac{34}{33}\]

    Correct Answer: A

    Solution :

    \[=\text{ }12+4=16\text{ cm}\] \[=\frac{3}{5}\]
    \[\cos \,\,(\alpha -\beta )=\sqrt{1-{{\sin }^{2}}\,\,(\alpha -\beta )}=\sqrt{1-\frac{25}{169}}\]\[=\sqrt{\frac{144}{169}}=\frac{12}{13}\]
    \[\therefore \]\[\tan \,\,(\alpha +\beta )=\frac{\sin \,\,(\alpha +\beta )}{\cos \,\,(\alpha +\beta )}=\left( \frac{3}{5}\times \frac{5}{4} \right)=\frac{3}{4}\]
    \[\tan \,\,(\alpha +\beta )=\frac{\sin \,\,(\alpha -\beta )}{\cos \,\,(\alpha -\beta )}=\frac{5}{13}\times \frac{13}{12}=\frac{5}{12}\]
    \[\therefore \]\[\tan \,\,(2\alpha )=\tan [(\alpha +\beta )+(\alpha -\beta )]\]
    \[=\frac{\tan \,\,(\alpha +\beta )+\tan \,\,(\alpha -\beta )}{1-\tan \,\,(\alpha +\beta )\cdot \tan \,\,(\alpha -\beta )}=\frac{\frac{3}{4}+\frac{5}{12}}{1-\frac{3}{4}\times \frac{5}{12}}=\frac{56}{33}\]
               


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