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visualizing complex vector based on eulerโ€™s formular

๐Ÿ™…โ€โ™‚๏ธํœด๋Œ€ํฐ์œผ๋กœ ๋ณผ ๋•Œ ํ˜น์‹œ ๊ธ€์ž๋‚˜ ์ˆซ์ž๊ฐ€ ํ™”๋ฉด์— ๋‹ค ์•ˆ๋‚˜์˜ค๋ฉด, ํœด๋Œ€ํฐ ๊ฐ€๋กœ๋กœ ๋Œ๋ฆฌ์‹œ๋ฉด ๋ฉ๋‹ˆ๋‹ค

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<๋ชฉ์ฐจ>

1. ๋“ค์–ด๊ฐ€๋ฉฐ 
2. ํšŒ์ „ํ–‰๋ ฌ์˜ ๊ณ ์œณ๊ฐ’, ๊ณ ์œ ๋ฒกํ„ฐ
3. ๋ณต์†Œ์ˆ˜์™€ ์˜ค์ผ๋Ÿฌ๊ณต์‹ 
4. ํšŒ์ „๋ณ€ํ™˜๊ณผ ๊ณ ์œ ๋ฒกํ„ฐ์˜ ์ƒํ˜ธ์ž‘์šฉ

1. ๋“ค์–ด๊ฐ€๋ฉฐ

์ด๋ฒˆ์‹œ๊ฐ„์—๋Š” ํšŒ์ „ํ–‰๋ ฌ์˜ ๊ณ ์œณ๊ฐ’๊ณผ ๊ณ ์œ ๋ฒกํ„ฐ๊ฐ€ ์˜ค์ผ๋Ÿฌ์˜ ๊ณต์‹๊ณผ ์–ด๋–ค ์—ฐ๊ด€์ด ์žˆ๋Š”์ง€ ์•Œ์•„๋ณผ ๊ฒƒ์ž…๋‹ˆ๋‹ค.

Prerequisites

2. ํšŒ์ „ํ–‰๋ ฌ์˜ ๊ณ ์œณ๊ฐ’, ๊ณ ์œ ๋ฒกํ„ฐ

Desktop View Desktop View




Desktop View


๐ŸŽฒํšŒ์ „ํ–‰๋ ฌ์˜ ๊ณ ์œณ๊ฐ’ ๊ณ„์‚ฐ

\(A\vec{x} = \gamma \vec{x} \\ \begin{bmatrix} cos \theta & -sin \theta \\ sin \theta & cos \theta \end{bmatrix} \vec{x} = \gamma \vec{x}\)

$(A-\gamma I_2)\vec{x} = 0$

์ฐธ๊ณ ๋กœ ์œ„์˜ ํ–‰๋ ฌ์„ B๋ผ ํ•˜๋ฉด ์—ญํ–‰๋ ฌ์ธ \(B^{-1}\)์„ ๊ฐ€์ง€๋ฉด ์•ˆ๋จ
\(det \left( \gamma I_2 -A \right) \\ \rightarrow det\begin{pmatrix} cos \theta-\gamma & -sin \theta \\ sin \theta & cos \theta-\gamma \end{pmatrix} = 0 \\ \rightarrow (cos \theta-\gamma)^2 + sin^2\theta = 0 \\ \rightarrow \gamma^2 - 2cos \theta \gamma + cos^2\theta + sin^2 \theta = 0 \\ \gamma^2 -2cos\theta\gamma + 1 = 0\)


์—ฌ๊ธฐ์„œ 2์ฐจ๋ฐฉ์ •์‹์˜ ๊ทผ์˜๊ณต์‹์„ ์ด์šฉํ•˜์ž
๊ทผ์˜๊ณต์‹ \(\rightarrow\) \(ax^2+bx+c=0\) ์ผ ๋•Œ, ย  \(x = \frac{-b \pm \sqrt{b^2-4ac}}{2a}\)
\(\therefore \gamma = \frac{2cos \theta \pm \sqrt{4cos^2\theta-4}}{2} \\ \rightarrow \gamma^2 = cos^2\theta \pm (cos^2 \theta-1)\)

์ž ๊น ์•„๋ž˜์‹ ์ฐธ๊ณ !
$sin^2\theta+cos^2\theta=1$๋ฅผ ์ด์šฉํ•˜์—ฌ ์ด๋ ‡๊ฒŒ ๋ณ€ํ˜•ํ•ด๋ณด์ž $ \color{pink}{\Rightarrow} $ \(cos^2\theta-1=-sin^2\theta\)
\(\gamma^2 = cos^2\theta \pm -sin^2\theta \\ \gamma = cos\theta \pm isin\theta\)

์˜ค์ผ๋Ÿฌ ๊ณต์‹์œผ๋กœ ๋ณ€ํ™˜ ๊ฐ€๋Šฅํ•˜๊ฒ ๋„ค
\(e^{\pm i\theta} = cos\theta \pm isin\theta\)
์ผ๋‹จ ์˜ค์ผ๋Ÿฌ๊ณต์‹์— ๋Œ€ํ•œ ์ž์„ธํ•œ ์„ค๋ช…์€ ๊ณ ์œ ๋ฒกํ„ฐ ๊ตฌํ•˜๊ณ  ์ง„ํ–‰ํ•˜๊ฒ ๋‹ค



๐ŸงฉํšŒ์ „ํ–‰๋ ฌ์˜ ๊ณ ์œ ๋ฒกํ„ฐ ๊ณ„์‚ฐ

case 1) ย  \(\gamma = cos\theta + isin\theta\)

\(Ax = \gamma x \\ \begin{bmatrix} cos \theta & -sin \theta \\ sin \theta & cos \theta \end{bmatrix} \vec{x} = (cos\theta + isin\theta) \vec{x}\)
์—ฌ๊ธฐ์„œ \(\gamma x\)๋ฅผ \(\gamma I_2 x\)๋กœ ๋ฐ”๊ฟ”์ฃผ์ž
\(\rightarrow\) \((cos\theta + isin\theta) \begin{bmatrix} 1 & 0 \\ 0 & 1 \end{bmatrix} = \begin{bmatrix} (cos\theta + isin\theta) & 0 \\ 0 & (cos\theta + isin\theta) \end{bmatrix}\)

๊ทธ๋Ÿฌ๋ฉด \(Ax = \gamma I_2 x\)์ด ๋˜๋Š”๋ฐ, ์—ฌ๊ธฐ์„œ ์šฐ๋ณ€์„ ์ขŒ๋ณ€์œผ๋กœ ๋„˜๊ธฐ๋ฉด?
\(\Rightarrow (A-\gamma I_2)x = 0 \\ \Rightarrow \begin{bmatrix} cos \theta-cos \theta-isin\theta & -sin \theta \\ sin \theta & cos \theta - cos \theta- isin\theta \end{bmatrix} \begin{bmatrix} x_1 \\ x_2 \end{bmatrix} = 0 \\ \Rightarrow \begin{bmatrix} -isin\theta & -sin \theta \\ sin \theta & - isin\theta \end{bmatrix} \begin{bmatrix} x_1 \\ x_2 \end{bmatrix} = 0\)

Ax=0 ๊ผด์ด ๋˜๋Š”๋ฐ ์—ฌ๊ธฐ์„œ ์—ฐ๋ฆฝ๋ฐฉ์ •์‹ ํ’€๋ฉด ์•„๋ž˜์ฒ˜๋Ÿผ ๊ณ ์œ ๋ฒกํ„ฐ๊ฐ€ ๋‚˜์˜จ๋‹ค
๋”ฐ๋ผ์„œ ย  \(\vec{x} = \begin{bmatrix} i \\ 1 \end{bmatrix}\)


case 2) ย  \(\gamma = cos\theta - isin\theta\)

์œ„์™€ ๋˜‘๊ฐ™์ด ๊ณ„์‚ฐํ•ด์ฃผ๋ฉด \(\vec{x} = \begin{bmatrix} -i \\ 1 \end{bmatrix}\)




3. ๋ณต์†Œ์ˆ˜์™€ ์˜ค์ผ๋Ÿฌ๊ณต์‹

์šฐ์„  ๋ณต์†Œ์ˆ˜๋ฅผ ์•Œ๊ธฐ ์œ„ํ•ด์„œ ์‹ค์ˆ˜๋ถ€์™€ ํ—ˆ์ˆ˜๋ฅผ ์•Œ์•„์•ผ ํ•œ๋‹ค.
\(\color{pink}{\Rightarrow}\) \(x+iy\)
์ฐธ ๋ณต์†Œ์ˆ˜ ๋ฒกํ„ฐ ๋‚ด์ (๊ธธ์ด)์„ ๊ตฌํ•˜๋Š” ๊ฑด ์˜ˆ๋ฅผ ๋“ค์–ด \(v = \begin{bmatrix} 1 \\ i \end{bmatrix}\)๋ผ๊ณ  ํ•  ๋•Œ,
\(||v|| = \sqrt{v\cdot \bar v} = \sqrt{(1,i)\cdot(1,-i)} = \sqrt{1+1} \\ \therefore \sqrt2\)

์ด์ œ \(x+iy\) ์„ animation์œผ๋กœ ๋‚˜ํƒ€๋‚ด๋ฉด ์•„๋ž˜์™€ ๊ฐ™๋‹ค
์œ„์˜ ๋‚ด์šฉ์—์„œ \(x+iy\)์™€ \(\sqrt{(1,i)\cdot(1,i)}\)๋ฅผ ์ดํ•ดํ–ˆ๋‹ค๋ฉด, ์•„๋ž˜ ์˜์ƒ์ด ๋ฌด์Šจ ๋ง์ธ์ง€ ๋ฐ”๋กœ ์ดํ•ดํ•  ๊ฒƒ์ด๋‹ค
Desktop View

1์—์„œ i๋ฅผ ๊ณฑํ•˜๋ฉด 90๋„ ๋Œ์•„์„œ i,
i์—์„œ i ๊ณฑํ•˜๋ฉด 90๋„ ๋˜ ๋Œ์•„์„œ -1
์ฆ‰ ์Šค์นผ๋ผ๋ฐฐ๋ฅผ ์ƒ๊ฐํ•ด๋ณด๋ฉด ์Œ์ˆ˜๋ฅผ ๊ณฑํ•˜๋Š” ๊ฒƒ์€ ๋ฐ˜๋Œ€๋ฐฉํ–ฅ์œผ๋กœ์˜ ๋ณ€ํ™˜,
๋ณต์†Œ์ˆ˜๋ฅผ ๊ณฑํ•˜๋Š” ๊ฑด ํšŒ์ „ ์„ ์˜๋ฏธํ•œ๋‹ค.
ํ˜น์‹œ ์ง€๊ธˆ๋„ ๋ฌด์Šจ๋ง์ธ์ง€ ์ž˜ ๋ชฐ๋ผ๋„ ๊ดœ์ฐฎ๋‹ค.
๋ฐ‘์˜ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ์กฐ์ž‘ํ•ด๋ณด๊ณ  ์˜์ƒ์„ ๋ณด๋ฉด 100ํผ ์ดํ•ดํ•  ๊ฒƒ์ด๋‹ค


๐Ÿ“Eulerโ€™s Formula

\(e^{\pm i\theta} = rcos\theta \pm risin\theta\)

์—ฌ๊ธฐ์„œ \(e^{i\theta}\)์˜ ์˜๋ฏธ:
\(\color{pink}{\Rightarrow}\) r(๋ฐ˜์ง€๋ฆ„)์ด๋ผ๋Š” ์ˆซ์ž๋ฅผ ์ž„์˜์˜ \(\theta\)๋ผ๋””์•ˆ ๋งŒํผ ํšŒ์ „์‹œํ‚ค๊ฒ ๋‹ค

Desktop View

Desktop View

์ง„์งœ ์™„์ „ ์‰ฌ์šด ์ดํ•ด \(\Rightarrow sin90=1\), ย  \(cos90 = 0\)์ด๋‹ˆ๊นŒ,
์˜ค์ผ๋Ÿฌ ๊ณต์‹์„ ์ฐธ๊ณ ํ•˜์—ฌ ์‹œ๋ฎฌ๋ ˆ์ด์…˜์„ ๋Œ๋ฆด ๋•Œ \(n\): 1~20 ๋ฒ”์œ„์ธ๋ฐ,
n์ด ์ปค์งˆ์ˆ˜๋ก sin ๊ฐ’์ด ์ปค์ง€๋‹ˆ๊นŒ 1์— ๊ฐ€๊นŒ์›Œ์ง„๋‹ค
์ด์ œ ์˜ค์ผ๋Ÿฌ ๊ณต์‹์—์„œ \(\theta\)๊ฐ€ ์ปค์งˆ ๋•Œ์˜ ๊ด€๊ณ„๊ฐ€ ๋ˆˆ์— ๋ณด์ด์ง€ ์•Š๋Š”๊ฐ€?

(ํ˜น์‹œ n์ด ์ปค์ง€๋Š”๊ฑฐ๋ž‘ 1์— ๊ฐ€๊นŒ์›Œ์ง€๋Š”๊ฒŒ ๋ฌด์Šจ๋ง์ธ์ง€ ๋ชจ๋ฅด๊ฒ ์œผ๋ฉด ์•„๋ž˜ ๋งํฌ๋กœ ๋“ค์–ด๊ฐ€์ž)

ส• ยทแดฅยทส” ย  ๋ฐ˜๊ฐ‘๊ณฐ




4. ํšŒ์ „๋ณ€ํ™˜๊ณผ ๊ณ ์œ ๋ฒกํ„ฐ์˜ ์ƒํ˜ธ์ž‘์šฉ

์šฐ์„  ํ•œ๊ณ„์ ์œผ๋กœ ๋ณต์†Œ ๊ณ ์œ ๋ฒกํ„ฐ๋Š” ์‹œ๊ฐํ™”ํ•˜๋Š”๊ฒŒ ๋งค์šฐ ์–ด๋ ต๋‹ค.
๋ณต์†Œ์ˆ˜ ์ž์ฒด๊ฐ€ ์ด๋ฏธ 2์ฐจ์›์˜ ์ˆ˜๋ผ์„œ ๊ทธ๋ ‡๋‹ค
์ฆ‰ $R^2$์˜ ๋ณต์†Œ๋ฒกํ„ฐ๋Š” ์‹ค์ˆ˜ 4๊ฐœ๊ฐ€ ์žˆ์–ด์•ผ ํ‘œํ˜„ ๊ฐ€๋Šฅํ•˜๋‹ค ย  ๋ฌด์Šจ๋ง์ธ์ง€ RG?
ํ•˜์ง€๋งŒ ์šฐ๋ฆฌ๊ฐ€ ์•„๊นŒ ์œ„์—์„œ ์–ป์€ ๊ณ ์œ ๋ฒกํ„ฐ 2๊ฐœ์ธ \(\vec{v} = \begin{bmatrix} \pm i \\ 1 \end{bmatrix}\)๋กœ 2์ฐจ์› ๋ณต์†Œ๋ฒกํ„ฐ๋ฅผ ์‹œ๊ฐํ™” ํ•ด๋ณด์ž!

Desktop View

$c_1$: ์ฒซ ๋ฒˆ์งธ ์„ฑ๋ถ„

$c_2$: ๋‘ ๋ฒˆ์งธ ์„ฑ๋ถ„

๐Ÿ˜Ž์‹œ๊ฐํ™”

์šฐ์„  ๋ฐ˜์ง€๋ฆ„(r)์„ 1์ด๋ผ ํ•˜๊ฒ ๋‹ค ๊ทธ๋Ÿฌ๋ฉด ์˜ค์ผ๋Ÿฌ๊ณต์‹์€ ์•„๋ž˜์™€ ๊ฐ™์ด ๋œ๋‹ค
\(e^{\pm i\theta} = cos\theta \pm isin\theta\)

  • ์—ฌ๊ธฐ์„œ ๊ณ ์œ ๋ฒกํ„ฐ์— ๋Œ€ํ•œ ์„ ํ˜•๋ณ€ํ™˜์€ ๋”ฑ ๊ณ ์œณ๊ฐ’ ๋งŒํผ๋งŒ ์ƒ์ˆ˜๋ฐฐํ•œ๋‹ค
  • ๊ณ ์œณ๊ฐ’ $e^{i\theta}$์™€ $e^{-i\theta}$๋Š” ์‹œ๊ณ„ or ๋ฐ˜์‹œ๊ณ„๋ฐฉํ–ฅ์œผ๋กœ $\theta$๋ผ๋””์•ˆ ๋งŒํผ์˜ ํšŒ์ „์„ ์˜๋ฏธํ•œ๋‹ค
    (๋ณต์†Œ๋ฒกํ„ฐ, $\bar v_1$๊ณผ $\bar v_2$์— ๋Œ€ํ•ด ๊ณ ์œณ๊ฐ’ ๋งŒํผ ์ƒ์ˆ˜๋ฐฐ
    $\Rightarrow$ ๊ณ ์œ ๋ฒกํ„ฐ๋ฅผ ์‹œ๊ณ„ or ๋ฐ˜์‹œ๊ณ„๋กœ $\theta$๋ผ๋””์•ˆ ๋งŒํผ ํšŒ์ „)

์•„๋ž˜ ์‹œ๋ฎฌ๋ ˆ์ด์…˜ 2๊ฐœ๋ฅผ ์กฐ์ž‘ํ•˜๋ฉด์„œ ์šฐ์ธก ์ƒ๋‹จ์— ๋‚˜์˜ค๋Š” ๊ฐ๋„๋„ ํ™•์ธ ๊ฐ€๋Šฅํ•˜๋‹ค

\(\gamma_1 = e^{i\theta}\)์ผ ๋•Œ ํšŒ์ „๋ณ€ํ™˜๊ณผ ๊ณ ์œ ๋ฒกํ„ฐ์˜ ์ƒํ˜ธ ์ž‘์šฉ

\(\gamma_2 = e^{-i\theta}\)์ผ ๋•Œ ํšŒ์ „๋ณ€ํ™˜๊ณผ ๊ณ ์œ ๋ฒกํ„ฐ์˜ ์ƒํ˜ธ ์ž‘์šฉ






์ฐธ๊ณ 

๊ณต๋Œ์ด์˜ ์ˆ˜ํ•™์ •๋ฆฌ๋…ธํŠธ ย ย ย  ํšŒ์ „ ํ–‰๋ ฌ์˜ ๊ณ ์œณ๊ฐ’, ๊ณ ์œ ๋ฒกํ„ฐ (๋ณต์†Œ ๊ณ ์œณ๊ฐ’, ๊ณ ์œ ๋ฒกํ„ฐ)์˜ ์˜๋ฏธ

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