Manipal Engineering Manipal Engineering Solved Paper-2008

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

    A)  cut at right angles

    B)  touch each other

    C)  cut at an angle\[\frac{\pi }{3}\]

    D)  cut at an angle\[\frac{\pi }{4}\]

    Correct Answer: A

    Solution :

    Given curves are                 \[{{x}^{3}}-3x{{y}^{2}}+2=0\] and        \[3{{x}^{2}}y-{{y}^{3}}-2=0\] On differentiating w.r.t. x, we get                 \[{{\left( \frac{dy}{dx} \right)}_{{{c}_{1}}}}=\frac{{{x}^{2}}-{{y}^{2}}}{2xy}\] and        \[{{\left( \frac{dy}{dx} \right)}_{{{c}_{2}}}}=\frac{-2xy}{{{x}^{2}}-{{y}^{2}}}\] Now,     \[{{\left( \frac{dy}{dx} \right)}_{{{c}_{1}}}}\times {{\left( \frac{dy}{dx} \right)}_{{{c}_{2}}}}=-1\] Hence, the two curves cut at right angles.


You need to login to perform this action.
You will be redirected in 3 sec spinner