JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2010

  • question_answer
        If\[sin\text{ }x+cosec\text{ }x=2,\]then\[{{\sin }^{n}}x+\cos e{{c}^{n}}x\]is equal to

    A)  2                                            

    B)  \[{{2}^{n}}\]

    C)  \[{{2}^{n-1}}\]                                 

    D)  \[{{2}^{n-2}}\]

    Correct Answer: A

    Solution :

                    \[sin\text{ }x+cosec\text{ }x=2\] \[\sin x+\frac{1}{\sin x}=2\] \[{{\sin }^{2}}x+1=2\sin x\] \[\Rightarrow \]               \[si{{n}^{2}}x+1=2\text{ }sin\text{ }x\] \[\Rightarrow \]               \[{{(\sin x-1)}^{2}}=0\] \[\Rightarrow \]               \[\sin x=1\] \[\Rightarrow \]               \[\cos ec\,x=1\] Now,     \[{{\sin }^{n}}x+\cos e{{c}^{n}}x={{(1)}^{n}}+{{(1)}^{n}}\]                                 \[=1+1=2\]


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