CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2001

  • question_answer
    The equations\[x=\frac{{{e}^{t}}+{{e}^{-t}}}{2},y=\frac{{{e}^{t}}-{{e}^{-t}}}{2}\]where t is real number, represents:

    A)  an ellipse       

    B)         a parabola

    C)  a hyperbola   

    D)         a circle

    E)  none of these

    Correct Answer: C

    Solution :

    \[\because \]\[x=\frac{{{e}^{t}}+{{e}^{-t}}}{2}\]and\[y=\frac{{{e}^{t}}-{{e}^{-t}}}{2}\] \[\because \]     \[{{({{e}^{t}}+{{e}^{-t}})}^{2}}={{({{e}^{t}}-{{e}^{-t}})}^{2}}+4\] \[\Rightarrow \]\[\frac{{{({{e}^{t}}+{{e}^{-t}})}^{2}}}{4}=\frac{{{({{e}^{t}}-{{e}^{-t}})}^{2}}}{4}+1\] \[\Rightarrow \]\[{{x}^{2}}={{y}^{2}}+1\Rightarrow {{x}^{2}}-{{y}^{2}}=1\] This shows the given equation represents a hyperbola.


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