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

  • question_answer
    The shortest distance between the lines \[\frac{x-2}{3}=\frac{y+3}{4}=\frac{z-1}{5}\] and \[\frac{x-5}{1}=\frac{y-1}{2}=\frac{z-6}{3}\] is

    A)  \[3\]

    B)  \[2\]

    C)  \[1\]

    D)  \[0\]

    Correct Answer: D

    Solution :

    Shortest distance \[=\frac{\left| \begin{matrix}    {{x}_{2}}-{{x}_{1}} & {{y}_{2}}-{{y}_{1}} & {{z}_{2}}-{{z}_{1}}  \\    {{a}_{1}} & {{b}_{1}} & {{c}_{1}}  \\    {{a}_{2}} & {{b}_{2}} & {{c}_{2}}  \\ \end{matrix} \right|}{\sqrt{\Sigma {{({{m}_{1}}{{n}_{2}}-{{m}_{2}}{{n}_{1}})}^{2}}}}\] Now, \[\left| \begin{matrix}    {{x}_{2}}-{{x}_{1}} & {{y}_{2}}-{{y}_{1}} & {{z}_{2}}-{{z}_{1}}  \\    {{a}_{1}} & {{b}_{1}} & {{c}_{1}}  \\    {{a}_{2}} & {{b}_{2}} & {{c}_{2}}  \\ \end{matrix} \right|\] \[=\left| \begin{matrix}    5-2 & 1+3 & 6-1  \\    3 & 4 & 5  \\    1 & 2 & 3  \\ \end{matrix} \right|=\left| \begin{matrix}    3 & 4 & 5  \\    3 & 4 & 5  \\    1 & 2 & 3  \\ \end{matrix} \right|\] \[=0\] (\[\because \]   two  rows are identical) \[\therefore \] Shortest distance \[=0\]


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