J & K CET Engineering J and K - CET Engineering Solved Paper-2006

  • question_answer
    The   curve   with   parametric   equation \[x={{e}^{t}}+{{e}^{-t}}\] and \[y={{e}^{t}}-{{e}^{-t}}\] is

    A)  a circle        

    B)  an ellipse

    C)  a hyperbola    

    D)  a parabola

    Correct Answer: C

    Solution :

    Given parametric equations are \[x={{e}^{t}}+{{e}^{-t}}\] and \[y={{e}^{t}}-{{e}^{-t}},\] now squaring and subtracting, we get \[{{x}^{2}}-{{y}^{2}}={{e}^{2t}}+{{e}^{-2t}}+2{{e}^{t-t}}\] \[-({{e}^{2t}}+{{e}^{-2t}}-2{{e}^{t-t}})\] \[\Rightarrow \] \[{{x}^{2}}-{{y}^{2}}=4\] \[\Rightarrow \] \[{{x}^{2}}-{{y}^{2}}=4\] Which is the equations of a hyperbola.


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