Mathematics 9709 · AS & A Level · Complex numbers

Complex numbers — practice question

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

Find the modulus of $z$ and its argument.

(ii(a))[4]

The complex conjugate of $z$ is written as $z^*$. With working shown, express $2z + z^*$ 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, express the expression $\frac{iz^*}{z}$ in the form $x + iy$, where $x$ and $y$ are real.

(iii)[3]

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

Worked solution & mark scheme

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

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