Complex Numbers - Using Complex Numbers to Deduce Trigonometric Values

Complex Numbers - Using Complex Numbers to Deduce Trigonometric Values

The complex number \(w\) has modulus \(\sqrt2\) and argument \(-3\pi/4\), and the complex number \(z\) has modulus \(2\) and argument \(-\pi/3\). Given that \(w=-1-i\) and \(z=1-\sqrt3\,i\).

  1. Find the exact values of the modulus and argument of \(wz\).
  2. By first expressing \(w\) and \(z\) in the form \(x+y\mathbf{i}\), find the exact real and imaginary part of \(wz\).
  3. Hence show that \(\sin \frac{\pi }{12}=\frac{\sqrt{3}-1}{2\sqrt{2}}\) .

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Answer:(a) \(|wz|=2\sqrt2,\ \arg(wz)=11\pi/12\). (b) \(\operatorname{Re}(wz)=-(1+\sqrt3),\ \operatorname{Im}(wz)=\sqrt3-1\). (c) \(\sin(\pi/12)=(\sqrt3-1)/(2\sqrt2)\).

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