Mathematics 9709 · AS & A Level · Complex numbers

Complex numbers — practice question

The complex number $-\sqrt{3} + i$ is called $u$.
(a)[2]

Write $u$ in the form $re^{i\theta}$, where $r > 0$ and $-\pi < \theta \leq \pi$, and give the exact values of $r$ and $\theta$.

(b)[2]

Hence establish that $u^6$ is real and state its value.

(c(i))[4]

On an Argand diagram sketch, shade the region made up of points for complex numbers $z$ satisfying $0 \leq \arg(z - u) \leq \frac{\pi}{4}$ and $\Re z \leq 2$.

(c(ii))[2]

Determine the greatest value of $|z|$ for points in the shaded region, and give your answer correct to 3 significant figures.

Worked solution & mark scheme

This 10-mark question has a full step-by-step worked solution and mark scheme. One marking point: State, or make clear, that $r=2$.

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