2017年7月21日金曜日

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6章(曲線をえがくこと)、2(曲線をえがくこと)、練習問題11、12.を取り組んでみる。


    1. x軸との交点。

      ( 3 2 ,0 )

      y軸との交点は(0, -3)。


    2. 臨界点。

      f'( x )= 2( 3x+1 )( 2x3 )3 ( 3x+1 ) 2 = 11 ( 3x+1 ) 2

      臨界点は無い。


    3. 増加する範囲。

      { 1 3 }

    4. 減少する範囲は無い。


    5. 極大点、極小点は無い。


    6. lim x± f( x )= 2 3

    7. x= 1 3


    1. x軸との交点。

      x( x 3 +4 )=0 x=0, 4 1 3 ( 0,0 ),( 4 1 3 ,0 )

      y軸との交点は(0, 0)。


    2. f'( x )=4 x 3 +4 =4( x 3 +1 ) x=1

    3. 1x

    4. x1

    5. 極大点は無い。

      極小点はx = -1。


    6. lim x± f( x )=


    7. 未定義の区間は無い。

コード(Emacs)

Python 3

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

from sympy import pprint, symbols, solve, Derivative, Limit, S, tan, plot

x = symbols('x')
fs = [(2 * x - 3) / (3 * x + 1),
      x ** 4 + 4 * x]

for i, f in enumerate(fs, 9):
    print(f'{i}.')
    pprint(f)
    pprint(solve(f))
    pprint(f.subs({x: 0}))
    d = Derivative(f, x, 1)
    pprint(d)
    f1 = d.doit()
    pprint(f1)
    pprint(solve(f1))
    for x0 in [S.Infinity, -S.Infinity]:
        l = Limit(f, x, x0)
        pprint(l)
        pprint(l.doit())
    print()

p = plot(fs[1], show=False, legend=True)
p.save('sample11.svg')

入出力結果(Terminal, IPython)

$ ./sample11.py
9.
2⋅x - 3
───────
3⋅x + 1
[3/2]
-3
d ⎛2⋅x - 3⎞
──⎜───────⎟
dx⎝3⋅x + 1⎠
  3⋅(2⋅x - 3)      2   
- ─────────── + ───────
            2   3⋅x + 1
   (3⋅x + 1)           
[]
    ⎛2⋅x - 3⎞
lim ⎜───────⎟
x─→∞⎝3⋅x + 1⎠
2/3
     ⎛2⋅x - 3⎞
 lim ⎜───────⎟
x─→-∞⎝3⋅x + 1⎠
2/3

10.
 4      
x  + 4⋅x
⎡           2/3    2/3        2/3    2/3     ⎤
⎢     2/3  2      2   ⋅√3⋅ⅈ  2      2   ⋅√3⋅ⅈ⎥
⎢0, -2   , ──── - ─────────, ──── + ─────────⎥
⎣           2         2       2         2    ⎦
0
d ⎛ 4      ⎞
──⎝x  + 4⋅x⎠
dx          
   3    
4⋅x  + 4
⎡    1   √3⋅ⅈ  1   √3⋅ⅈ⎤
⎢-1, ─ - ────, ─ + ────⎥
⎣    2    2    2    2  ⎦
    ⎛ 4      ⎞
lim ⎝x  + 4⋅x⎠
x─→∞          
∞
     ⎛ 4      ⎞
 lim ⎝x  + 4⋅x⎠
x─→-∞          
∞

$

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="-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">
<br>
<label for="dx0">dx0 = </label>
<input id="dx0" type="number" min="0" value="0.1">

<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="sample11.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'),
    input_dx0 = document.querySelector('#dx0'),
    inputs = [input_r, input_dx, input_x1, input_x2, input_y1, input_y2,
             input_dx0],
    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 f = (x) => (2 * x - 3) / (3 * x + 1),
    f1 = (x) => 11 / (3 * x + 1) ** 2,
    g = (x0) => (x) => f1(x0) * (x - x0) + f(x0);
    
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),
        dx0 = parseFloat(input_dx0.value);

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

    let points = [],
        lines = [[-1/3, y1, -1/3, y2, 'red']],
        fns = [[f, 'green']],
        fns1 = [],
        fns2 = [[g, 'orange']];

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

                if (Math.abs(y) < Infinity) {
                    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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