Let a complex number be w=1−3i. Let another complex number z be such that ∣zw∣=1 and arg(z)−arg(w)=2π. Then the area of the triangle with vertices origin, z and w, is equal to
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Official solution
∣w∣=1+3=2, and ∣zw∣=1⟹∣z∣=21. Since the angle between z and w is 2π,
\[\text{Area}=\frac12|z||w|\sin\frac\pi2=\frac12\cdot\frac12\cdot2=\frac12.\]