BCECE Engineering BCECE Engineering Solved Paper-2014

  • question_answer
    If t is a parameter, then \[x=a\left( t+\frac{1}{t} \right)\] and\[y=b\left( t-\frac{1}{t} \right)\]represent

    A) an ellipse            

    B) a circle

    C) a pair of straight lines

    D) a hyperbola

    Correct Answer: D

    Solution :

     Given equations can be rewritten as \[\frac{x}{a}=t+\frac{1}{t}\]             and         \[\frac{y}{b}=t-\frac{1}{t}\] On squaring and subtracting, we get \[{{\left( \frac{x}{a} \right)}^{2}}-{{\left( \frac{y}{b} \right)}^{2}}={{\left( t+\frac{1}{t} \right)}^{2}}-{{\left( t-\frac{1}{t} \right)}^{2}}\] \[=\left( {{t}^{2}}+\frac{1}{{{t}^{2}}}+2 \right)-\left( {{t}^{2}}+\frac{1}{{{t}^{2}}}-2 \right)=4\] \[\Rightarrow \frac{{{x}^{2}}}{4{{a}^{2}}}-\frac{{{y}^{2}}}{4{{b}^{2}}}=1\]


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