Mathematics 9709 · AS & A Level · Complex numbers

Complex numbers — practice question

Let $u$ represent the complex number $1 - i$.
(i)[2]

Show your working and, without using a calculator, express $\frac{i}{u}$ in the form $x + iy$, where $x$ and $y$ are real.

(ii)[4]

On an Argand diagram, sketch the loci for complex numbers $z$ that satisfy the equations $|z - u| = |z|$ and $|z - i| = 2$.

(iii)[3]

Find the argument of each complex number shown by the two intersection points of the loci in part (ii).

Worked solution & mark scheme

This 9-mark question has a full step-by-step worked solution and mark scheme. One marking point: Substitute $u$ into $\frac{i}{u}$, then multiply the numerator and denominator by $1+i$

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