Q.
If z1,z2,z3,z4 are four distinct complex numbers representing the vertices of a quadrilateral taken in order such that z1−z4=z2−z3 and arg(z2−z1z4−z1)=2π, then quadrilateral is a
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Complex Numbers and Quadratic Equations
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Solution:
Since z1−z4=z2−z3 ⇒2z1+z3=2z1+z4
i.e., diagonal AC and DB bisect each other. ∴ABCD is a parallelogram.
Again ∠BAD=Arg(z2−z1z4−z1)=π/2
which means parallelogram is a rectangle.