JEE Main & Advanced JEE Main Online Paper (Held on 9 April 2013)

  • question_answer
                    A value of \[x\] for which \[\sin ({{\cot }^{-1}}(1+x))=\cos ({{\tan }^{-1}}x),\] is:                   JEE Main Online Paper (Held On 09 April 2013)

    A)                 \[-\frac{1}{2}\]                 

    B)                 1                

    C)                 0                

    D)                 \[\frac{1}{2}\]                

    Correct Answer: A

    Solution :

                    \[\sin \,[{{\cot }^{-1}}(1+x)]=\cos ({{\tan }^{-1}}x)\]                 \[\sin \,\left[ {{\sin }^{-1}}\frac{1}{\sqrt{2+2x+{{x}^{2}}}} \right]=\cos \,\left( {{\cos }^{-1}}\frac{1}{\sqrt{1+{{x}^{2}}}} \right)\]                 \[\frac{1}{\sqrt{{{x}^{2}}+2x+2}}=\frac{1}{\sqrt{1+{{x}^{2}}}}\]                 \[{{x}^{2}}+2x+2=1+{{x}^{2}}\]                 \[2x=-1\]                 \[x=-\frac{1}{2}\]                


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