VIT Engineering VIT Engineering Solved Paper-2007

  • question_answer
    If \[\overrightarrow{b}\] is a unit vector, then\[(\overrightarrow{a}\cdot \overrightarrow{b})\overrightarrow{b}+\overrightarrow{b}\times (\overrightarrow{a}\times \overrightarrow{b})\]is:

    A)  \[{{\left| \,\overrightarrow{a}\, \right|}^{2}}\overrightarrow{b}\]

    B)  \[\left| \,\overrightarrow{a}\cdot \overrightarrow{b}\, \right|\,\overrightarrow{a}\]

    C)  \[\overrightarrow{a}\]

    D)  \[\overrightarrow{b}\]

    Correct Answer: C

    Solution :

    \[(\vec{a}\cdot \vec{b})\,\vec{b}+\vec{b}\times (\vec{a}\times \vec{b})\] \[=(\vec{a}\cdot \vec{b})\,\vec{b}+(\vec{b}\cdot \vec{b})\,\vec{a}-(\vec{a}\cdot \vec{b})\,\vec{b}\] \[=\vec{a}\]


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