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SSC Sample Paper Mock Test-9 SSC CGL Tear-II Paper-1

  • question_answer
    The value of \[{{\cos }^{2}}45{}^\circ -{{\sin }^{2}}15{}^\circ \]is

    A)  \[\frac{\sqrt{3}}{2}\]    

    B)  \[\frac{\sqrt{3}}{1}\]

    C)  \[\frac{1}{\sqrt{3}}\]    

    D)  \[\frac{\sqrt{3}}{4}\]

    Correct Answer: D

    Solution :

    \[{{\cos }^{2}}45{}^\circ -{{\sin }^{2}}15{}^\circ =\cos \,\,(45{}^\circ +15{}^\circ )\cos \,\,(45{}^\circ -15{}^\circ )\]         \[=\cos 60{}^\circ \cos 30{}^\circ =\frac{1}{2}\times \frac{\sqrt{3}}{2}=\frac{\sqrt{3}}{4}\]


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