2025 SJI P2 Q4

2025 SJI P2 Q4

IB Year 5 | Grade 11
8 marks

The complex numbers \(z\) and \(w\) satisfy the equations

\[\frac wz=3\mathrm i,\qquad z^*-w=1+5\mathrm i.\]

  1. Find \(z\) and \(w\) in the form \(a+b\mathrm i\), where \(a,b\in\mathbb Z\).[5]
  2. The points representing \(z\) and \(w\) can be represented on an Argand diagram as \(P_1\) and \(P_2\) respectively.
    1. State the ratio of their moduli \(\dfrac{|w|}{|z|}\).
    2. The line segment \([OP_1]\) is rotated by \(\theta^\circ\) anticlockwise and scaled by factor \(k\) to obtain \([OP_2]\). Find value of \(\theta\) and of \(k\).[3]

Solution:

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Answer:(a) \(z=-2+\mathrm i,w=-3-6\mathrm i\) (b)(i) \(3\), (ii) \(\theta=90,k=3\)

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