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JEE Main & Advanced Mathematics Vector Algebra Question Bank Scaler or Dot product of two vectors and its application

  • question_answer
    If \[4i+j-k\] and \[3i+mj+2k\] are at right angle, then \[m=\]                                     [Karnataka CET 2002]

    A)             ? 6

    B)             ? 8

    C)             ? 10

    D)             ? 12

    Correct Answer: C

    Solution :

               Since angle between the vectors is \[{{90}^{o}}\], therefore dot product of the vectors will be zero                                                       or \[(4\mathbf{i}+\mathbf{j}-\mathbf{k})\,.\,(3\mathbf{i}+m\mathbf{j}+2\mathbf{k})=0\]                                 or \[12+m-2=0\] or \[m=-10.\]


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