## 2017年12月6日水曜日

### 数学 - Python - JavaScript - 線型代数 - 複素数、複素ベクトル空間 - 極形式(絶対値と偏角)

1. $\alpha =r\mathrm{cos}\theta +ir\mathrm{sin}\theta$

絶対値。

$\begin{array}{}\left|\alpha \right|\\ =\sqrt{{r}^{2}{\mathrm{cos}}^{2}\theta +{r}^{2}{\mathrm{sin}}^{2}\theta }\\ =\sqrt{{r}^{2}\left({\mathrm{cos}}^{2}\theta +{\mathrm{sin}}^{2}\theta \right)}\\ =\sqrt{{r}^{2}}\\ =r\end{array}$

偏角。

$\mathrm{cos}\theta \ne 0$

の場合。

$\begin{array}{}\mathrm{tan}\left(\mathrm{arg}\alpha \right)\\ =\frac{r\mathrm{sin}\theta }{r\mathrm{cos}\theta }\\ =\frac{\mathrm{sin}\theta }{\mathrm{cos}\theta }\\ =\mathrm{tan}\theta \\ \mathrm{arg}\alpha =\theta \end{array}$
$\mathrm{cos}\theta =0$

の場合。

$\begin{array}{}\alpha =ir\mathrm{sin}\theta \\ \mathrm{arg}\alpha =\theta \end{array}$

（証明終）

コード(Emacs)

Python 3

#!/usr/bin/env python3
from sympy import pprint, symbols, sqrt, sin, cos, solve, I

θ = symbols('θ', real=True)
r = symbols('r', positive=True)

z = r * (cos(θ) + I * sin(θ))

for t in [z, abs(z)]:
pprint(t)
print()


$./sample2.py r⋅(ⅈ⋅sin(θ) + cos(θ)) ___________________ ╱ 2 2 r⋅╲╱ sin (θ) + cos (θ)$


HTML5

<div id="graph0"></div>
<pre id="output0"></pre>
<label for="r0">r = </label>
<input id="r0" type="number" min="0" value="0.5">
<label for="dx">dx = </label>
<input id="dx" type="number" min="0" step="0.0001" value="0.001">
<br>
<label for="x1">x1 = </label>
<input id="x1" type="number" value="-10">
<label for="x2">x2 = </label>
<input id="x2" type="number" value="10">
<br>
<label for="y1">y1 = </label>
<input id="y1" type="number" value="-10">
<label for="y2">y2 = </label>
<input id="y2" type="number" value="10">
<br>
<label for="r1">r1 = </label>
<input id="r1" type="number" min="0" value="5">
<label for="θ0">θ0 = </label>
<input id="θ0" type="number" min="0" value="1">

<button id="draw0">draw</button>
<button id="clear0">clear</button>

<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/d3/4.2.6/d3.min.js" integrity="sha256-5idA201uSwHAROtCops7codXJ0vja+6wbBrZdQ6ETQc=" crossorigin="anonymous"></script>

<script src="sample2.js"></script>


JavaScript

let div0 = document.querySelector('#graph0'),
pre0 = document.querySelector('#output0'),
width = 600,
height = 600,
btn0 = document.querySelector('#draw0'),
btn1 = document.querySelector('#clear0'),
input_r = document.querySelector('#r0'),
input_dx = document.querySelector('#dx'),
input_x1 = document.querySelector('#x1'),
input_x2 = document.querySelector('#x2'),
input_y1 = document.querySelector('#y1'),
input_y2 = document.querySelector('#y2'),
input_r1 = document.querySelector('#r1'),
input_θ0 = document.querySelector('#θ0'),
inputs = [input_r, input_dx, input_x1, input_x2, input_y1, input_y2],
p = (x) => pre0.textContent += x + '\n',
range = (start, end, step=1) => {
let res = [];
for (let i = start; i < end; i += step) {
res.push(i);
}
return res;
};

let fx = (a, x, y) => x * Math.cos(a) - y * Math.sin(a),
fy = (a, x, y) => x * Math.sin(a) + y * Math.cos(a);

let draw = () => {
pre0.textContent = '';

let r = parseFloat(input_r.value),
dx = parseFloat(input_dx.value),
x1 = parseFloat(input_x1.value),
x2 = parseFloat(input_x2.value),
y1 = parseFloat(input_y1.value),
y2 = parseFloat(input_y2.value),
r1 = parseFloat(input_r1.value),
θ0 = parseFloat(input_θ0.value);

if (r === 0 || dx === 0 || x1 > x2 || y1 > y2) {
return;
}

let points = [],
real = r1 * Math.cos(θ0),
imag = r1 * Math.sin(θ0),
lines = [[real, y1, real, y2, 'red'],
[x1, imag, x2, imag, 'green'],
[0, 0, real, imag, 'blue']],
fns = [],
fns1 = [],
fns2 = [];

fns
.forEach((o) => {
let [f, color] = o;
for (let x = x1; x <= x2; x += dx) {
let y = f(x);

points.push([x, y, color]);
}
});

fns2
.forEach((o) => {
let [f, color] = o;

for (let x = x1; x <= x2; x += dx0) {
let g = f(x);
lines.push([x1, g(x1), x2, g(x2), color]);
}
});

let xscale = d3.scaleLinear()
.domain([x1, x2])
let yscale = d3.scaleLinear()
.domain([y1, y2])

let xaxis = d3.axisBottom().scale(xscale);
let yaxis = d3.axisLeft().scale(yscale);
div0.innerHTML = '';
let svg = d3.select('#graph0')
.append('svg')
.attr('width', width)
.attr('height', height);

svg.selectAll('line')
.data([[x1, 0, x2, 0], [0, y1, 0, y2]].concat(lines))
.enter()
.append('line')
.attr('x1', (d) => xscale(d[0]))
.attr('y1', (d) => yscale(d[1]))
.attr('x2', (d) => xscale(d[2]))
.attr('y2', (d) => yscale(d[3]))
.attr('stroke', (d) => d[4] || 'black');

svg.selectAll('circle')
.data(points)
.enter()
.append('circle')
.attr('cx', (d) => xscale(d[0]))
.attr('cy', (d) => yscale(d[1]))
.attr('r', r)
.attr('fill', (d) => d[2] || 'green');

svg.append('g')
.attr('transform', translate(0, ${height - padding})) .call(xaxis); svg.append('g') .attr('transform', translate(${padding}, 0))
.call(yaxis);

[fns, fns1, fns2].forEach((fs) => p(fs.join('\n')));
};

inputs.forEach((input) => input.onchange = draw);
btn0.onclick = draw;
btn1.onclick = () => pre0.textContent = '';
draw();