CAIE A-Level Mathematics A2 3.9.8 Complex Numbers Questions
Practise sketching complex-number loci and regions, then finding extrema of modulus, argument and coordinates.
- Syllabus
- 2028–2030
- Course
- Mathematics 9709
- Level
- A2
Practise sketching complex-number loci and regions, then finding extrema of modulus, argument and coordinates.
On a single Argand diagram sketch the loci given by the equations |z-3+2 i|=2 and ∣w−3+2i∣=∣w+3−4i∣ where z and w are complex numbers.
Official markscheme sketch for Q7(a): circle centre (3,-2), radius 2, with the perpendicular bisector locus.
Draw the circle |z-3+2i|=2 with centre (3,-2) and radius 2. The second locus is the perpendicular bisector of the segment from (3,-2) to (-3,4). Mark (-3,4) or the midpoint (0,1), and draw the perpendicular bisector, equivalently the line y=x+1.
B1 for the circle centre (3,-2). B1FT for a circle of radius 2 with centre not at the origin. B1 for the point (-3,4) or midpoint (0,1). B1FT for the perpendicular bisector of the line joining (-3,4) and the centre of the circle.
Hence find the least value of |z-w| for points on these loci. Give your answer in an exact form.
Carry out a correct method for finding the least value of |z-w|
(Distance (3,-2) to (0,1))-2.
Obtain answer 18−2 or 32−2