ci) First you are told that you have two right angles at A and also note that

. How is that useful because now you can write 1 for OA and

for AB and AC which will come in handy.
There use Pythag to find the length of

which will come in handy.
There we will use the mod arg form to find that
+i\sin\left(\frac{\pi}{3}\right)\right)z_{1})
. Noticing that
+i\sin\left(\frac{\pi}{3}\right)\right))
is the extension and rotation of
Therefore,
For part ii do the same but this time you will have
+i\sin\left(\frac{-\pi}{3}\right)\right)z_{1})
giving us
I mean you can apply parallelogram law for this but I think it is overkill.

by calculation will give us

as the imaginary

will perish after you subtract them.