JEE Main & Advanced Mathematics Differentiation Question Bank Partial Differentiation

  • question_answer
    If \[z=\frac{y}{x}\left[ \sin \frac{x}{y}+\cos \left( 1+\frac{y}{x} \right) \right]\], then \[x\frac{\partial z}{\partial x}=\]                                                                                          [EAMCET 2002]

    A)            \[y\frac{\partial z}{\partial y}\]

    B)            \[-y\frac{\partial z}{\partial y}\]

    C)            \[2y\frac{\partial z}{\partial y}\]

    D)            \[2y\frac{\partial z}{\partial x}\]

    Correct Answer: B

    Solution :

                       Since z is homogeneous in x, y of order ?0?.                    \[\therefore \]  By Euler?s  theorem \[x\frac{\partial z}{\partial x}+y\frac{\partial z}{\partial y}=\] 0                     Þ \[x\frac{\partial z}{\partial x}=-y\frac{\partial z}{\partial y}\]


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