CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2006

  • question_answer
    If \[\vec{a}\] is vector perpendicular to both \[\vec{b}\] and \[\vec{c}\], then :

    A)  \[\vec{a}+(\vec{b}+\vec{c})=\vec{0}\] 

    B)  \[\vec{a}\times (\vec{b}+\vec{c})=\vec{0}\]

    C)  \[\vec{a}\times (\vec{b}\times \vec{c})=\vec{0}\]         

    D)  \[\vec{a}\,\,.\,\,(\vec{b}\times \vec{c})=\vec{0}\]

    Correct Answer: C

    Solution :

    Now, \[\vec{a}\times (\vec{b}\times \vec{c})\] \[=(\vec{a}\,.\,\vec{b})\,\vec{c}-(\vec{a}\,.\,\vec{c})\,\vec{b}\] \[=\vec{0}-\vec{0}\]                       (\[\because \] \[\vec{a}\bot \vec{b}\] and \[\vec{a}\bot \vec{c}\] \[=\vec{0}\]


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