Manipal Engineering Manipal Engineering Solved Paper-2011

  • question_answer
    The two curves\[{{x}^{3}}-3x{{y}^{2}}+2=0\]and\[3{{x}^{2}}y-{{y}^{3}}=2\]

    A)  cut at right angles

    B)  touch each other

    C)  cut at an angle\[\pi /3\]

    D)  cut at an angle\[\pi /4\]

    Correct Answer: A

    Solution :

    Given curves are                 \[{{x}^{3}}-3x{{y}^{2}}+2=0\]                      ... (i) and        \[3{{x}^{2}}y-{{y}^{3}}-2=0\]                      ... (ii) On differentiating Eqs. (i) and (ii), with respect to\[x\], we get                 \[\left( \frac{dy}{dx} \right){{c}_{1}}=\frac{{{x}^{2}}-{{y}^{2}}}{2xy}\] and        \[\left( \frac{dy}{dx} \right){{c}_{2}}=\frac{2xy}{{{x}^{2}}-{{y}^{2}}}\]                 \[{{\left( \frac{dy}{dx} \right)}_{{{C}_{1}}}}\times {{\left( \frac{dy}{dx} \right)}_{{{C}_{2}}}}=-1\]


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