AMU Medical AMU Solved Paper-2011

  • question_answer
    If vectors A and B are such that |A+B|=|A|=|B|, then |A-B| may be equated to

    A)  \[\frac{\sqrt{3}}{2}\left| \text{A} \right|\]                         

    B)  |A|

    C)  \[\frac{\sqrt{2}}{2}\left| \text{A} \right|\]                         

    D)   \[\sqrt{3}\]|A|

    Correct Answer: D

    Solution :

                     \[{{\left| A+B \right|}^{2}}={{\left| A \right|}^{2}}+{{\left| B \right|}^{2}}+2AB\Rightarrow 2AB={{\left| A \right|}^{2}}\]                 or \[-2AB={{\left| A \right|}^{2}}\]                          \[\left[ \left| A+B \right|=\left| A \right|=\left| B \right| \right]\]                 \[\therefore {{\left| A-B \right|}^{2}}={{\left| A \right|}^{2}}+{{\left| A \right|}^{2}}+{{\left| A \right|}^{2}}=3{{\left| A \right|}^{2}}\]


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