CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2009

  • question_answer
    The angle between the line \[\frac{3x-1}{3}=\frac{y+3}{-1}\]\[=\frac{5-2z}{4}\]and the plane\[3x-3y-6z=10\]is equal to

    A)  \[\frac{\pi }{6}\]                                             

    B)  \[\frac{\pi }{4}\]

    C)  \[\frac{\pi }{3}\]                             

    D)         \[\frac{\pi }{2}\]

    E)  \[\frac{2\pi }{3}\]

    Correct Answer: D

    Solution :

    Given lines and planes are \[\frac{3x-1}{3}=\frac{y+3}{-1}=\frac{5-2z}{4}\] Or           \[\frac{x-\frac{1}{3}}{1}=\frac{y+3}{-1}=\frac{\left( z-\frac{5}{2} \right)}{-2}\] and        \[3x-3y-6z=0\] \[\Rightarrow \]            \[x-y-2z=0\] Here,    \[{{a}_{1}}=1,{{b}_{1}}=-1,{{c}_{1}}=-2\] and        \[{{a}_{2}}=1,{{b}_{2}}=-1,{{c}_{2}}=-2\] \[\therefore \]  \[\sin \theta =\frac{{{a}_{1}}{{a}_{2}}+{{b}_{1}}{{b}_{2}}+{{c}_{1}}{{c}_{2}}}{\sqrt{a_{1}^{2}+b_{1}^{2}+c_{1}^{2}}\sqrt{a_{2}^{2}+b_{2}^{2}+c_{2}^{2}}}\]                 \[=\frac{1\times 1+(-1)\times (-1)+(-2)\times (-2)}{\sqrt{1+1+4}\sqrt{1+1+4}}\]                 \[=\frac{6}{\sqrt{6}\sqrt{6}}=1\] \[\Rightarrow \]               \[\theta =\frac{\pi }{2}\]


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