JCECE Engineering JCECE Engineering Solved Paper-2014

  • question_answer
    Angle between the vectors \[\sqrt{3}(\mathbf{a}\times \mathbf{b})\] and\[b-(\mathbf{a}\cdot \mathbf{b})\mathbf{a}\]

    A) \[\frac{\pi }{2}\]                                              

    B) \[\frac{\pi }{4}\]

    C)  \[0\]                                    

    D)  \[\frac{\pi }{3}\]

    Correct Answer: A

    Solution :

    Let\[\mathbf{A}=\sqrt{3}(\mathbf{a}\times \mathbf{b})\]and\[\mathbf{B}=\mathbf{b}-(\mathbf{a}\cdot \mathbf{b})\mathbf{a}\] A is the vector perpendicular to the plane of\[\mathbf{a},\,\,\mathbf{b}\]. B is the vector lies in the plane of\[\mathbf{a},\,\,\mathbf{b}\]. \[\therefore \]  \[\mathbf{A}\cdot \mathbf{B}=0\] or the angle between them is\[\frac{\pi }{2}\].


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