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

  • question_answer
    \[|\mathbf{a}\times \mathbf{b}{{|}^{2}}+\,{{(\mathbf{a}\,.\,\mathbf{b})}^{2}}=\]                 [MP PET 1989, 97, 2004]

    A)                 \[(\mathbf{a}\times \mathbf{a})\,.\,(\mathbf{b}\times \mathbf{b})\]

    B)                 \[(\mathbf{a}\,.\,\mathbf{a})\,(\mathbf{b}\,.\,\mathbf{b})\]

    C)                 \[|\,(\mathbf{a}\times \mathbf{b})\,|\,\,(\mathbf{a}\,.\,\mathbf{b})\]

    D)                 \[2\,(\mathbf{a}\,.\,\mathbf{b})\,(\mathbf{a}\,.\,\mathbf{b})\]

    Correct Answer: B

    Solution :

                    We know \[{{(\mathbf{a}\times \mathbf{b})}^{2}}+{{(\mathbf{a}\,.\,\mathbf{b})}^{2}}={{a}^{2}}{{b}^{2}}=(\mathbf{a}\,.\,\mathbf{a})(\mathbf{b}\,.\,\mathbf{b})\].


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