JEE Main & Advanced Mathematics Differentiation Question Bank Derivative at a point Standard Differentiation

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

    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: B

    Solution :

               \[{{\sin }^{-1}}\sqrt{1-x}={{\sin }^{-1}}\sqrt{1-{{(\sqrt{x})}^{2}}}={{\cos }^{-1}}\sqrt{x}\]            \[\therefore y=2{{\cos }^{-1}}\sqrt{x}\]or\[\frac{dy}{dx}=2.\frac{-1}{\sqrt{1-x}}.\frac{1}{2\sqrt{x}}\]etc.            Aliter: \[y={{\sin }^{-1}}\sqrt{1-x}+{{\cos }^{-1}}\sqrt{x}\]            Þ \[\frac{dy}{dx}=\frac{1}{\sqrt{1-1+x}}.\frac{-1}{2\sqrt{1-x}}-\frac{1}{\sqrt{1-x}}.\frac{1}{2\sqrt{x}}\]                 \[=\frac{-2}{2\sqrt{x}\sqrt{1-x}}=\frac{-1}{\sqrt{x}\sqrt{1-x}}\].


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