JCECE Engineering JCECE Engineering Solved Paper-2012

  • question_answer
    The locus of the middle points of chords of the parabola \[{{y}^{2}}=8x\] drawn through the vertex is a parabola whose

    A)  focus is\[(2,\,\,0)\]        

    B)  latusrectum\[=8\]

    C)  focus is\[(0,\,\,2)\]        

    D)  latusrectum\[=4\]

    Correct Answer: D

    Solution :

    If the middle point of a chord is \[(\alpha ,\,\,\beta ),\] then                 \[\alpha =\frac{2{{t}^{2}}+0}{2},\,\,\beta =\frac{4t+0}{2}\] On eliminating\[t\], we get                 \[\alpha ={{\left( \frac{\beta }{2} \right)}^{2}}\] \[\therefore \]Locus is\[x=\frac{{{y}^{2}}}{4}\] \[\Rightarrow \]               \[{{y}^{2}}=4x\] This is the equation of parabola with latusrectum\[4\]


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