## 2018年10月2日火曜日

### 数学 - Python - JavaScript - 解析学 - 積分 - 積分の計算 - 三角関数に関する積分(置換積分法、逆正弦関数、微分、不定積分)

1. $\begin{array}{}\int \frac{{x}^{2}}{{\left({a}^{2}-{x}^{2}\right)}^{\frac{3}{2}}}\mathrm{dx}\\ =\int {x}^{2}{\left({a}^{2}-{x}^{2}\right)}^{-\frac{3}{2}}\mathrm{dx}\\ =f{\left({a}^{2}-{x}^{2}\right)}^{-\frac{1}{2}}-\int \frac{1}{\sqrt{{a}^{2}-{x}^{2}}}\mathrm{dx}\\ =\frac{x}{\sqrt{{a}^{2}-{x}^{2}}}-\mathrm{arcsin}\left(\frac{x}{a}\right)\end{array}$

コード(Emacs)

Python 3

#!/usr/bin/env python3
from sympy import pprint, symbols, Integral, plot, Rational

print('23.')

a, x = symbols('a, x')
f = x ** 2 / (a ** 2 - x ** 2) ** Rational(3, 2)
I = Integral(f, x)
for t in [I, I.doit().simplify()]:
pprint(t)
print()

a0 = 2
p = plot(f.subs({a: a0}), I.doit().simplify().subs(
{a: a0}), legend=True, show=False)
colors = ['red', 'green']
for i, c in enumerate(colors):
p[i].line_color = c
p.save('sample23.svg')


$./sample23.py 23. ⌠ ⎮ 2 ⎮ x ⎮ ──────────── dx ⎮ 3/2 ⎮ ⎛ 2 2⎞ ⎮ ⎝a - x ⎠ ⌡ ⎧ │ 2│ ⎪ ⎛x⎞ ⅈ⋅x │x │ ⎪ⅈ⋅acosh⎜─⎟ - ───────────────── for │──│ > 1 ⎪ ⎝a⎠ _________ │ 2│ ⎪ ╱ 2 │a │ ⎪ ╱ x ⎪ a⋅ ╱ -1 + ── ⎪ ╱ 2 ⎪ ╲╱ a ⎨ ⎪ ⎛x⎞ x ⎪ - asin⎜─⎟ + ──────────────── otherwise ⎪ ⎝a⎠ ________ ⎪ ╱ 2 ⎪ ╱ x ⎪ a⋅ ╱ 1 - ── ⎪ ╱ 2 ⎪ ╲╱ a ⎩$


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="0.001" value="0.001">
<br>
<label for="x1">x1 = </label>
<input id="x1" type="number" value="-5">
<label for="x2">x2 = </label>
<input id="x2" type="number" value="5">
<br>
<label for="y1">y1 = </label>
<input id="y1" type="number" value="-5">
<label for="y2">y2 = </label>
<input id="y2" type="number" value="5">

<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="sample23.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_n0 = document.querySelector('#n0'),
inputs = [input_r, input_dx, input_x1, input_x2, input_y1, input_y2],
p = (x) => pre0.textContent += x + '\n';

let f = (x) => x ** 2 / Math.sqrt((2 ** 2 - x ** 2) ** 3),
g = (x) => x / Math.sqrt(2 ** 2 - x ** 2) - Math.asin(x / 2),
fns = [[f, 'red'],
[g, 'green']];

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);

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

let points = [],
lines = [];

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

points.push([x, y, 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].forEach((fs) => p(fs.join('\n')));
};

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