2020 ACJC CA2 Q3

2020 ACJC CA2 Q3

5 marks
Tutorial

The complex number \(z\) is given by \(z=\frac{{{\left( k+ka\mathbf{i} \right)}^{2}}}{{{\left( 1-a\mathbf{i} \right)}^{2}}}\), where \(a\) and \(k\) are positive real numbers.

  1. Given that \(\left| z \right|=3\), find the exact value of \(k\).[2]
  2. Given that \(\arg \left( z \right)=\frac{2\pi }{3}\), find the exact value of \(a\).[3]

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Answer:(i) \(k=\sqrt3\) (ii) \(a=\dfrac{\sqrt3}{3}\)

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