VIT Engineering VIT Engineering Solved Paper-2010

  • question_answer
    Domain of the function \[f(x)={{\log }_{x}}\cos x,\]is

    A)  \[\left( -\frac{\pi }{2},\frac{\pi }{2} \right)-\{\,1\,\}\]

    B)  \[\left[ -\frac{\pi }{2},\frac{\pi }{2} \right]-\{\,1\,\}\]

    C)  \[\left( -\frac{\pi }{2},\frac{\pi }{2} \right)\]

    D)  None of these

    Correct Answer: D

    Solution :

    We have the function \[f(x)=lo{{g}_{x}}\cos x\] \[f(x)\] is defined for\[\cos \,x>0,\] \[x>0,\] \[x\ne 1\] \[\because \] \[\cos x>0\] \[\Rightarrow \] \[-\frac{\pi }{2}<x<\frac{\pi }{2}\] Also, \[x>0,\,\,x\ne 1\] \[\therefore \] Domain of\[f\]is\[\left( 0,\,\,\frac{\pi }{2} \right)-(1)\].


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