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JEE Main & Advanced Mathematics Three Dimensional Geometry Question Bank System of Co-ordinates, Direction cosines and direction ratios, Projection

  • question_answer
    The projections of a line on the co-ordinate axes are 4, 6, 12. The direction cosines of the line are

    A)            \[\frac{2}{7},\frac{3}{7},\frac{6}{7}\]

    B)            2, 3, 6

    C)            \[\frac{2}{11},\frac{3}{11},\frac{6}{11}\]

    D)            None of these

    Correct Answer: A

    Solution :

               Direction cosines \[=\left( \frac{4}{\sqrt{16+36+144}},\frac{6}{14},\frac{12}{14} \right)\]            or \[\left( \frac{2}{7},\frac{3}{7},\frac{6}{7} \right)\].


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