RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    If\[y={{\sin }^{-1}}\sqrt{(1-x)}+{{\cos }^{-1}}\sqrt{x},\]then\[\frac{dy}{dx}\]is equal to

    A)  \[\frac{-1}{\sqrt{x(1-x)}}\]          

    B)  \[\frac{1}{\sqrt{x(1+x)}}\]

    C)  \[\frac{1}{\sqrt{x(1-x)}}\]       

    D)  None of these

    Correct Answer: A

    Solution :

     \[y={{\sin }^{-1}}(\sqrt{1-x})+{{\cos }^{-1}}\sqrt{x}\] \[\therefore \] \[\frac{dy}{dx}=\frac{1}{\sqrt{1-{{(\sqrt{1-x})}^{2}}}}.\frac{-1}{2\sqrt{1-x}}\] \[+\left( \frac{-1}{\sqrt{1-{{(\sqrt{x})}^{2}}}} \right).\frac{1}{2\sqrt{x}}\] \[=\frac{1}{2\sqrt{1-1+x}\sqrt{1-x}}-\frac{1}{2\sqrt{1-x}\sqrt{x}}\] \[=\frac{-1}{2\sqrt{x}\sqrt{1-x}}-\frac{1}{2\sqrt{1-x}\sqrt{x}}\] \[=-\frac{2}{2\sqrt{x}\sqrt{1-x}}=-\frac{1}{\sqrt{x(1-x)}}\]


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