Multiplication as a rotation of the complex plane

Multiplication as a rotation of the complex plane

IB Year 6 | Grade 12

Two complex numbers are given by \(z=2+2i\) and \(\omega=i\).

  1. Express \(z\) and \(\omega\) in exponential form.
  2. Hence,
    (i) find \(z\omega\) in exponential form,
    (ii) describe the transformation that takes place when \(z\) is multiplied by \(\omega\).

Solution:

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Answer:(a) \(z=2\sqrt2\,e^{i\pi/4},\ \omega=e^{i\pi/2}\) (b)(i) \(z\omega=2\sqrt2\,e^{i3\pi/4}\) (b)(ii) Anticlockwise rotation through \(\frac{\pi}{2}\) about the origin.

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