2017年10月3日火曜日

学習環境

解析入門 原書第3版 (S.ラング(著)、松坂 和夫(翻訳)、片山 孝次(翻訳)、岩波書店)の第2部(微分と基本的な関数)、第7章(逆関数)、4(逆正接関数)、練習問題17、18、19、20、21.を取り組んでみる。


  1. d dx ( arcsinx ) = 1 1 x 2 f( x ) = 1 1 1 2 ( x 1 2 )+arcsin 1 2 = 1 1 2 ( x 1 2 )+ π 4 = 2 x1+ π 4

  2. d dx ( arccosx ) = 1 1 x 2 f( x ) = 1 1 1 2 ( x 1 2 )+arccos 1 2 = 2 x+1+ π 4

  3. d dx ( arctan2x ) = 1 1+4 x 2 ·2 = 2 1+4 x 2 f( x ) = 2 1+4· 3 4 ( x 3 2 )+arctan( 2· 3 2 ) = 2 4 ( x 3 2 )+arctan 3 = 1 2 x 3 4 + π 3

  4. d dx ( arctanx ) = 1 1+ x 2 f( x ) = 1 1+1 ( x+1 )+arctan( 1 ) = 1 2 x+ 1 2 π 4

  5. d dx ( arcsinx ) = 1 1 x 2 f( x ) = 1 1 1 4 ( x+ 1 2 )+arcsin( 1 2 ) = 2 3 x+ 1 3 π 6

コード(Emacs)

Python 3

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

from sympy import pprint, symbols, asin, acos, atan, Derivative, sqrt, Rational

x = symbols('x')
fs = [(asin(x), 1 / sqrt(2)),
      (acos(x), 1 / sqrt(2)),
      (atan(2 * x), sqrt(3) / 2),
      (atan(x), -1),
      (asin(x), -Rational(1, 2))]

for i, (f, x0) in enumerate(fs, 17):
    print(f'{i}.')
    D = Derivative(f, x, 1)
    f1 = D.doit()
    g = f1.subs({x: x0}) * (x - x0) + f.subs({x: x0})
    for t in [f, D, f1, g]:
        pprint(t)
        print()
    print()

入出力結果(Terminal, Jupyter(IPython))

$ ./sample17.py
17.
asin(x)

d          
──(asin(x))
dx         

      1      
─────────────
   __________
  ╱    2     
╲╱  - x  + 1 

   ⎛    √2⎞   π
√2⋅⎜x - ──⎟ + ─
   ⎝    2 ⎠   4


18.
acos(x)

d          
──(acos(x))
dx         

     -1      
─────────────
   __________
  ╱    2     
╲╱  - x  + 1 

     ⎛    √2⎞   π
- √2⋅⎜x - ──⎟ + ─
     ⎝    2 ⎠   4


19.
atan(2⋅x)

d            
──(atan(2⋅x))
dx           

   2    
────────
   2    
4⋅x  + 1

x   √3   π
─ - ── + ─
2   4    3


20.
atan(x)

d          
──(atan(x))
dx         

  1   
──────
 2    
x  + 1

x   π   1
─ - ─ + ─
2   4   2


21.
asin(x)

d          
──(asin(x))
dx         

      1      
─────────────
   __________
  ╱    2     
╲╱  - x  + 1 

2⋅√3⋅(x + 1/2)   π
────────────── - ─
      3          6


$

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="0.01">
<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="sample17.js"></script>

JavaScript

let div0 = document.querySelector('#graph0'),
    pre0 = document.querySelector('#output0'),
    width = 600,
    height = 600,
    padding = 50,
    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'),
    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 f1 = (x) => Math.asin(x),
    g1 = (x) => Math.sqrt(2) * x - 1 + Math.PI / 4,
    f2 = (x) => Math.acos(x),
    g2 = (x) => -Math.sqrt(2) * x + 1 + Math.PI / 4,
    f3 = (x) => Math.atan(2 * x),
    g3 = (x) => 1 / 2 * x - Math.sqrt(3) / 4 + Math.PI / 3,
    f4 = (x) => Math.atan(x),
    g4 = (x) => 1 / 2 * x + 1 / 2 - Math.PI / 4,
    f5 = (x) => Math.asin(x),
    g5 = (x) => 2 / Math.sqrt(3) * x + 1 / Math.sqrt(3) - Math.PI / 6;

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 = [[1 / Math.sqrt(2), y1, 1 / Math.sqrt(2), y2, 'red'],
                 [Math.sqrt(3) / 2, y1, Math.sqrt(3) / 2, y2, 'blue'],
                 [-1, y1, -1, y2, 'orange'],
                 [-1 / 2, y1, -1 / 2, y2, 'skyblue']],        
        fns = [[f1, 'red'],
               [g1, 'red'],
               [f2, 'green'],
               [g2, 'green'],
               [f3, 'blue'],
               [g3, 'blue'],
               [f4, 'orange'],
               [g4, 'orange'],
               [f5, 'skyblue'],
               [g5, 'skyblue']],
        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])
        .range([padding, width - padding]);
    let yscale = d3.scaleLinear()
        .domain([y1, y2])
        .range([height - padding, padding]);

    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();







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