Mathematics 9709 · AS & A Level · Complex numbers

Complex numbers — practice question

The complex number $z$ is defined by $z = (\sqrt{3}) + i.$
(i)[2]

Find the modulus and argument for $z.$

(ii(a))[4]

The complex conjugate of $z$ is written as $z^*$. With working shown, give $2z + z^*$ in the form $x + iy$, where $x$ and $y$ are real.

(ii(b))[4]

The complex conjugate of $z$ is written as $z^*$. With working shown, give $\frac{iz^*}{z}$ in the form $x + iy$, where $x$ and $y$ are real.

(iii)[3]

On a sketch of an Argand diagram with origin $O$, mark the points $A$ and $B$ to represent the complex numbers $z$ and $iz^*$ respectively. Show that angle $AOB = \frac{1}{6}\pi.$

Worked solution & mark scheme

This 13-mark question has a full step-by-step worked solution and mark scheme. One marking point: State the modulus as $2$

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