2024 RI P1 Q8

2024 RI P1 Q8

12 marks
Prelims

Do not use a calculator in answering this question.

  1. The complex number \(w\) is such that \(w=a+ib\), where \(a\) and \(b\) are non-zero real numbers. The complex conjugate of \(w\) is denoted by \({{w}^{*}}\). Given that
    \(w{{w}^{*}}=4-2i+2i{{w}^{*}}\),
    find the two possible values of \(w\).[4]
  2. The complex number \(z\) is given by \(z=\frac{1-\sqrt{3}i}{-1+i}\).
    1. Find \(\arg (z)\).[3]
    2. Find \(z\) in cartesian form \(x+iy\).[2]
    3. Hence find the value of \(\tan \frac{\pi }{12}\) in the form \(c+d\sqrt{3}\), where \(c\) and \(d\) are integers to be found.[3]

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Answer:(a) \(w = 1 + 3i\) or \(w = 1 - i\) (b)(i) \(\arg z = \frac{11\pi}{12}\) (b)(ii) \(z = -\frac{\sqrt{3}+1}{2} + \frac{\sqrt{3}-1}{2}i\) (b)(iii) \(\tan \frac{\pi}{12} = 2 - \sqrt{3}\)

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