Manipal Engineering Manipal Engineering Solved Paper-2008

  • question_answer
    The intercept made by the tangent to the curve\[y=\int_{0}^{x}{|t|}\,\,dt\],which is parallel to the line \[y=2x\], on x-axis is equal to

    A)  1            

    B)                         -2

    C)  2                            

    D)         None of these

    Correct Answer: A

    Solution :

    Given,\[y=\int_{0}^{x}{|t|}\,\,dt\] On differentiating w.r.t. x, we get                 \[\frac{dy}{dx}=|x|\] Since, the tangent is parallel to the line\[y=2x\] \[\therefore \]  \[|x|\,\,=2\Rightarrow x=\pm 2\] When\[x=2,\,\,y=\int_{0}^{2}{|t|}\,\,dt=\int_{0}^{2}{t\,\,dt}\]                 \[=\left[ \frac{{{t}^{2}}}{2} \right]_{0}^{2}=2\] When\[x=-2\],                 \[y=\int_{0}^{-2}{|t|}\,\,dt=\int_{-2}^{0}{t\,\,dt}\]                 \[=\left[ \frac{{{t}^{2}}}{2} \right]_{-2}^{0}=-2\] Then, tangent at (2, 2) is \[y-2=2(x-2)\] \[\Rightarrow \]               \[2x-y-2=0\] For,\[x-\]intercept, put\[y=0\], then\[x=1\] Also, tangent at (-2,-2) is                 \[y+2=2(x+2)\] \[\Rightarrow \,\,\,\,2x-y+2=0\] For\[x-\]intercept, put\[y=0\], then\[x=-1\].


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