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CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2001

  • question_answer
    If \[a\vec{i}+6\vec{j}-\vec{k}\]and \[7\vec{i}-3\vec{j}+17\vec{k}\]are perpendicular vectors, then the value of a is equal to:

    A)  5                            

    B)  7

    C)  4                            

    D)  3/2

    Correct Answer: A

    Solution :

    Two vectors perpendicular, therefore their dot product is zero \[(a\vec{i}+6\vec{j}-\vec{k})(7\vec{i}-3\vec{j}+17\vec{k})=0\]\[\Rightarrow \]\[7a-18-17=0\Rightarrow 7a=35\] \[a=5\]


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