Manipal Engineering Manipal Engineering Solved Paper-2010

  • question_answer
    If\[z=\tan (y+ax)+\sqrt{y-ax}\],   then\[{{z}_{xx}}-{{a}^{2}}{{z}_{yy}}\]is equal to

    A) \[0\]                                     

    B) \[2\]

    C) \[{{z}_{x}}+{{z}_{y}}\]   

    D)        \[{{z}_{x}}{{z}_{y}}\]

    Correct Answer: A

    Solution :

    We have,\[z=\tan (y+ax)+\sqrt{y-ax}\] \[\Rightarrow \]\[{{z}_{x}}=a{{\sec }^{2}}(y+ax)+\frac{(-a)}{2\sqrt{y-ax}}\] \[\Rightarrow \]\[{{z}_{xx}}=2{{a}^{2}}{{\sec }^{2}}(y+ax)\tan (y+ax)\]                                                 \[-\frac{{{a}^{2}}}{4}{{(y-ax)}^{-3/2}}\] and        \[{{z}_{y}}={{\sec }^{2}}(y+ax)+\frac{1}{2\sqrt{y-ax}}\] \[\Rightarrow \]\[{{z}_{yy}}=2{{\sec }^{2}}(y+ax)\tan (y+ax)\]                                                 \[-\frac{{{a}^{2}}}{4}{{(y-ax)}^{-3/2}}\] \[{{a}^{2}}{{z}_{yy}}\,=2{{a}^{2}}{{\sec }^{2}}(y+ax).\tan (y+ax)\]                                                 \[-\frac{{{a}^{2}}}{4}{{(y-ax)}^{-3/2}}\] Now,     \[{{z}_{xx}}-{{a}^{2}}{{z}_{yy}}=0\]


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