JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2006

  • question_answer
        The angle between the lines \[2x=3y=-\text{ }z\] and \[6x=-\text{ }y=-4z\]is

    A)  \[90{}^\circ \]                  

    B)  \[0{}^\circ \]  

    C)  \[30{}^\circ \]                  

    D)  \[45{}^\circ \]

    Correct Answer: A

    Solution :

                    The given equation of lines are\[2x=3y=-z\] \[\Rightarrow \]               \[\frac{x}{3}=\frac{y}{2}=\frac{z}{-6}\]                   ?.(i)       and        \[6x=-y=-4z\] \[\Rightarrow \]               \[\frac{x}{2}=\frac{y}{-12}=\frac{z}{-3}\]                               ?(ii) Let \[\theta \]be the angle between these two lines. \[\therefore \]  \[\cos \theta =\frac{(2)(3)+(2)(-12)+(-6)(-3)}{\sqrt{9+4+36}\sqrt{4+144+9}}\]                 \[=\frac{6-24+18}{7\sqrt{157}}=0\] \[\Rightarrow \]               \[\theta =90{}^\circ \]


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