RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    If complex numbers\[{{z}_{1}},{{z}_{2}}\]and\[{{z}_{3}}\]represents the vertices of an equilateral triangle such that\[|{{z}_{1}}|=|{{z}_{2}}|=|{{z}_{3}}|,\]then

    A)  \[{{z}_{1}}+{{z}_{2}}+{{z}_{3}}\le 0\]

    B)  \[{{z}_{1}}+{{z}_{2}}+{{z}_{3}}\ge 0\]

    C)  \[{{z}_{1}}+{{z}_{2}}+{{z}_{3}}=0\]

    D)  None of these

    Correct Answer: C

    Solution :

     Given, \[|{{z}_{1}}|=|{{z}_{2}}|=|{{z}_{3}}|\] Three points lies on the circle, whose centre is origin. Since, these points are vertices of an equilateral triangle so orthocentre and circumcentre will be same. Hence, \[\frac{{{z}_{1}}+{{z}_{2}}+{{z}_{3}}}{3}=0\] \[\Rightarrow \] \[{{z}_{1}}+{{z}_{2}}+{{z}_{3}}=0\]


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