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

  • question_answer
    If \[\mathbf{a}\times \mathbf{b}=\mathbf{b}\times \mathbf{c}\ne 0\] and \[\mathbf{a}+\mathbf{c}\ne 0,\] then                 [RPET 1999]

    A)                 \[(\mathbf{a}+\mathbf{c})\,\bot \,\mathbf{b}\]

    B)                 \[(\mathbf{a}+\mathbf{c})\,\,|\,\,|\,\,\mathbf{b}\]

    C)                 \[\mathbf{a}+\mathbf{c}=\mathbf{b}\]

    D)                 None of these

    Correct Answer: B

    Solution :

               \[\mathbf{a}\times \mathbf{b}=\mathbf{b}\times \mathbf{c}\Rightarrow (\mathbf{a}+\mathbf{c})\,\times \,\,\mathbf{b}=0,\]but \[\mathbf{a}+\mathbf{c}\ne 0\]                                 \[\Rightarrow \mathbf{a}+\mathbf{c}||\mathbf{b}.\]


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