2022 JPJC MYE P2 Q6

2022 JPJC MYE P2 Q6

10 marks
Mid Year Exam

Do not use a calculator in answering this question.

  1. It is given that \(w=1+\mathrm{i}\) and \(z=-\sqrt{3}-\mathrm{i}\).
    1. Find \(\frac{{{w}^{3}}}{z}\) in the form \(r\left( \cos \theta +\mathrm{i}\sin \theta \right)\), where \(r>0\) and \(-\pi <\theta \le \pi \).[3]
    2. Find the smallest positive integer value of \(n\), such that \({{\left( \frac{{{w}^{3}}}{z} \right)}^{n}}\) is real.[3]
  2. The complex number \(q\) is given by \(\frac{{{\mathrm{e}}^{\mathrm{i}\theta }}}{{{\mathrm{e}}^{-\mathrm{i}\theta }}-\mathrm{i}}\), where \(0 < \theta < \pi \).
    Show that the real part of \(q\) is \(\frac{1}{2}\left( 1-2\sin \theta  \right)\).[4]

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Answer:\(r = \sqrt{2}\), \(\theta = -\dfrac{5\pi}{12}\); smallest positive integer \(n = 12\); \(\text{Re}\hspace{0.1em}(q) = \frac{1}{2}(1 - 2\sin\theta)\)

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