CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2011

  • question_answer
    In Argand?s plane, the point corresponding to \[\frac{(1-i\sqrt{3})(1+i)}{(\sqrt{3}+i)}\]lies in

    A)  quadrant I                         

    B)  quadrant II

    C)  quadrant III                      

    D)  quadrant IV

    Correct Answer: D

    Solution :

    Given, \[\frac{(1-i\sqrt{3})(1+i)}{(\sqrt{3}+i)}=\frac{(1-i\sqrt{3}+i+\sqrt{3})(\sqrt{3}-i)}{(3+1)}\]                                                 \[(\because \,\,{{i}^{2}}=-1)\] \[=\frac{1}{4}.\{(1+\sqrt{3})+i\,(1-\sqrt{3})\}.(\sqrt{3}-i)\] \[=\frac{1}{4}.\{\sqrt{3}(1+\sqrt{3})+i\,(1-\sqrt{3})\sqrt{3}\]                                       \[-(1+\sqrt{3})\,i+(1-\sqrt{3})\}\] \[=\frac{1}{4}.\{\sqrt{3}+3+1-\sqrt{3})+(\sqrt{3}-3-1-\sqrt{3})i\}\] \[=\frac{1}{4}.\{4-4i\}=1-i\] The point \[(1-i)\] in Arg and plane is \[(1,-1)\] which lies in IV th quadrant.


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