J & K CET Engineering J and K - CET Engineering Solved Paper-2009

  • question_answer
    If in a hyperbola, the distance between the foci is 10 and the transverse axis has length 8, then the length of its latuserectum is

    A)  \[9\]

    B)  \[\frac{9}{2}\]

    C)  \[\frac{5}{4}\]

    D)  \[2\]

    Correct Answer: B

    Solution :

    Given,   \[2a=8\] and \[2ac=10\] \[\Rightarrow \] \[e=\frac{10}{8}=\frac{5}{4}\] Now, \[{{b}^{2}}={{a}^{2}}({{e}^{2}}-1)=16\left( \frac{25}{16}-1 \right)=9\] \[\Rightarrow \] \[b=\pm 3\] Hence, length of latuserectum \[=\frac{2{{b}^{2}}}{a}=\frac{2\times 9}{4}\] \[=\frac{9}{2}\]


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