CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2003

  • question_answer
    It\[{{\sin }^{-1}}x+{{\sin }^{-1}}y=\frac{\pi }{2},\]then\[\frac{dy}{dx}\]is equal to:

    A)  \[\frac{x}{y}\]                  

    B)         \[-\frac{x}{y}\]

    C)  \[\frac{y}{x}\]                  

    D)         \[-\frac{y}{x}\]

    E)  none of these

    Correct Answer: B

    Solution :

    \[{{\sin }^{-1}}x+{{\sin }^{-1}}y=\frac{\pi }{2}\] \[\Rightarrow \]               \[{{\sin }^{-1}}=\frac{\pi }{2}-{{\sin }^{-1}}y\] \[\Rightarrow \]               \[{{\sin }^{-1}}={{\cos }^{-1}}y\] \[\Rightarrow \]               \[y=\sqrt{1-{{x}^{2}}}\] On differentiating w.r.t.\[x,\]we get \[\frac{dy}{dx}=\frac{1}{2\sqrt{1-{{x}^{2}}}}(-2x)=-\frac{x}{y}\]


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