BCECE Engineering BCECE Engineering Solved Paper-2003

  • question_answer
    The points \[{{z}_{1}},{{z}_{2}},{{z}_{3}},{{z}_{4}}\]in the complex plane are the vertices of a parallelogram taken in order, iff:

    A) \[{{z}_{1}}+{{z}_{4}}={{z}_{2}}+{{z}_{3}}\]            

    B)                   \[{{z}_{1}}+{{z}_{3}}={{z}_{2}}+{{z}_{4}}\]           

    C)                   \[{{z}_{1}}+{{z}_{2}}={{z}_{3}}+{{z}_{4}}\]           

    D)                   none of these

    Correct Answer: B

    Solution :

    Key Idea: Diagonals of a parallelogram bisect each other at the same point. Since, the points \[{{z}_{1}},{{z}_{2}},{{z}_{3}}\]and \[{{z}_{4}}\] are the vertices of a parallelogram, therefore diagonals of a parallelogram bisect each other at a point   \[\frac{{{z}_{1}}+{{z}_{3}}}{2}=\frac{{{z}_{2}}+{{z}_{4}}}{2}\] \[\Rightarrow \]               \[{{z}_{1}}+{{z}_{3}}={{z}_{2}}+{{z}_{4}}\]


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