2018 EJC P1 Q6 (b)

2018 EJC P1 Q6 (b)

7 marks
Prelims

Do not use a calculator in answering this question.

It is given that \(q=-\sqrt{3}-\mathrm{i}\).

  1. Find an exact expression for \({{q}^{6}}\), giving your answer in the form \(r{{\mathrm{e}}^{\mathrm{i}\theta }}\), where \(r>0\) and \(0\le \theta <2\pi \).[3]
  2. Find the three smallest positive whole number values of \(n\) for which \(\frac{{{q}^{n}}}{{{q}^{*}}}\) is purely imaginary.[4]

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Answer:(i) \(q^6 = 64e^{i\pi}\) (ii) \(n = 2, 8, 14\)

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