2016 MJC P1 Q10

2016 MJC P1 Q10

11 marks
Prelims

Do not use a calculator in answering this question.

  1. Solve the simultaneous equations
    \(z=w+2\mathrm{i}-1\) and \({{z}^{2}}-\mathrm{i}w+\frac{5}{2}=0\),
    giving \(z\) and \(w\) in the form \(x+y\mathrm{i}\) where \(x\) and \(y\) are real.[5]
    1. Given that \(z=w-\frac{1}{w}\) where \(w=2(\cos \theta +\mathrm{i}\sin \theta )\), \(-\pi <\theta \le \pi \), express the real and imaginary parts \(z\) in terms of \(\theta \).[3]
    2. Hence show that the locus of \(z\) on an Argand diagram lies on the curve with cartesian equation \(\frac{{{x}^{2}}}{{{a}^{2}}}+\frac{{{y}^{2}}}{{{b}^{2}}}=1\) where \(a\) and \(b\) are constants.[3]

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Answer:(a) \(w = \frac{3}{2} - \frac{1}{2}i\), \(z = \frac{1}{2} + \frac{3}{2}i\); \(w = \frac{1}{2} - \frac{5}{2}i\), \(z = -\frac{1}{2} - \frac{1}{2}i\) (b)(ii) Ellipse

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