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Akbar Rahman 2021-10-14 15:17:27 +01:00
parent b19ef43cd8
commit 0deb97de3b
Signed by: alvierahman90
GPG Key ID: 20609519444A1269

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@ -19,8 +19,8 @@ tags: [ uni, nottingham, mmme1026, maths, complex_numbers ]
Where: Where:
- $x$ is the real part of $z$ (Re($z$)) - $x$ is the real part of $z$ (which you may seen written as $\Re(z) = x$ or Re$(z) = x$)
- $y$ is the imaginary part of $z$(Im($z$)) - $y$ is the imaginary part of $z$ (which you may seen written as $\Im(z) = y$ or Im$(z) = y$)
- Two complex numbers are equal if both their real and imaginary parts are equal - Two complex numbers are equal if both their real and imaginary parts are equal
@ -222,15 +222,24 @@ z_3 = z_1 z_2 &= (r_1e^{i\theta_1})(r_2e^{i\theta_2}) \\
Let $z = re^{i\theta}$. Consider $z^n$. Let $z = re^{i\theta}$. Consider $z^n$.
Since $z = r(\cos\theta + i\sin\theta)$,
\begin{align*} \begin{align*}
\text{Since } z = r(\cos\theta + i\sin\theta) \\
z^n &= r^n(\cos\theta + i\sin\theta)^n &\text{(1)} \\ z^n &= r^n(\cos\theta + i\sin\theta)^n &\text{(1)} \\
\text{But also} \\ \end{align*}
But also
\begin{align*}
z^n &= (re^{i\theta})^n \\ z^n &= (re^{i\theta})^n \\
&= r^n(e^{i\theta})^n \\ &= r^n(e^{i\theta})^n \\
&= r^ne^{in\theta} \\ &= r^ne^{in\theta} \\
&= r^n(\cos{n\theta} + i\sin{n\theta}) &\text{(2)} \\ &= r^n(\cos{n\theta} + i\sin{n\theta}) &\text{(2)} \\
\text{By equating (1) and (2), we find:}\\ \end{align*}
By equating (1) and (2), we find de Moivre's theorem:
\begin{align*}
r^n(\cos\theta +i\sin\theta)^n &= r^n(\cos{n\theta} + i\sin{n\theta}) \\
(\cos\theta +i\sin\theta)^n &= (\cos{n\theta} + i\sin{n\theta}) (\cos\theta +i\sin\theta)^n &= (\cos{n\theta} + i\sin{n\theta})
\end{align*} \end{align*}