2020年7月22日水曜日

学習環境

続 解析入門 (原書第2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章(ベクトルの微分)、1(微分係数)の練習問題8の解答を求めてみる。



    1. ( x , y ) = ( cos π 3 , sin π 3 ) + t ( cos π 3 , sin π 3 )
      ( x , y ) = ( 1 2 , 3 2 ) + t ( 1 2 , 3 2 )

    2. ( x , y ) = ( cos 3 · π 3 , sin 3 · π 3 ) + t ( cos 3 · π 3 , sin 3 · π 3 )
      ( x , y ) = ( - 1 , 0 ) + t ( - 1 , 0 )

コード

#!/usr/bin/env python3
from unittest import TestCase, main
from sympy import Matrix, Derivative, sin, cos, pi
from sympy.plotting import plot_parametric
from sympy.abc import t

print('8.')

a = Matrix([cos(t), sin(t)])
b = Matrix([cos(3 * t), sin(3 * t)])


class Test(TestCase):
    def test3(self):
        self.assertEqual(
            Derivative(a, t, 1).doit().dot(a), 0
        )

    def test4(self):
        self.assertEqual(
            Derivative(b, t, 1).doit().dot(b), 0
        )


p = plot_parametric(
    (cos(t), sin(t), (t, 0, 2 * pi)),
    (cos(pi / 3) + t * -sin(pi / 3),
     sin(pi / 3) + t * cos(pi / 3),
     (t, 0, 1)),
    (t * cos(pi / 3), t * sin(pi / 3), (t, -1, 1)),
    legend=True,
    show=False
)
colors = ['red', 'green', 'blue', 'brown', 'orange',
          'purple', 'pink', 'gray', 'skyblue', 'yellow']
for o, color in zip(p, colors):
    o.line_color = color
p.save('sample8_3.png')
p = plot_parametric(
    (cos(3 * t), sin(3 * t), (t, 0, 2 * pi / 3)),
    (cos(3 * pi / 3) + t * -3 * sin(3 * pi / 3),
     sin(3 * pi / 3) + t * 3 * cos(3 * pi / 3),
     (t, 0, 1)),
    (-1 * t, 0, (t, -1, 1)),
    legend=True,
    show=False
)
colors = ['red', 'green', 'blue', 'brown', 'orange',
          'purple', 'pink', 'gray', 'skyblue', 'yellow']
for o, color in zip(p, colors):
    o.line_color = color
p.save('sample8_4.png')
p.show()
if __name__ == "__main__":
    main()

入出力結果(Zsh、PowerShell、Terminal、Jupyter(IPython))

% ./sample8.py -v
8.
test3 (__main__.Test) ... ok
test4 (__main__.Test) ... ok

----------------------------------------------------------------------
Ran 2 tests in 0.006s

OK
%

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