JEE Main & Advanced Sample Paper JEE Main - Mock Test - 13

  • question_answer
    A curve satisfies the differential equation \[\sqrt{{{x}^{4}}-{{x}^{2}}}\,\,dy-\sqrt{{{y}^{4}}-{{y}^{2}}}\,\,dx=0.\]If \[y(0)=0,\]then curve also passes through the point

    A) \[(2,2)\]

    B)        \[(2,3)\]                  

    C) \[(2,-2)\]                 

    D)        None of these

    Correct Answer: A

    Solution :

         [a] We have \[\frac{dy}{dx}=\frac{\sqrt{{{y}^{4}}-{{y}^{2}}}}{\sqrt{{{x}^{4}}-{{x}^{2}}}}=\frac{y\sqrt{{{y}^{2}}-1}}{x\sqrt{{{x}^{2}}-1}}\] \[\Rightarrow \,\,\,\int{\frac{dy}{y\sqrt{{{y}^{2}}-1}}}\int{\frac{dx}{x\sqrt{{{x}^{2}}-1}}}\] \[\Rightarrow \,\,\,\,{{\sec }^{-1}}y={{\sec }^{-1}}x+c\] Since  \[y(0)=0,\,\,c=0.\] \[\therefore \,\,\,\,{{\sec }^{-1}}y={{\sec }^{-1}}\,\,x\] or \[y=x\] 


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