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学习笔记《Euler's formula》

学习笔记《Euler's formula》

作者: 马文Marvin | 来源:发表于2018-04-04 11:49 被阅读36次

欧拉公式建立了三角函数和复平面指数函数之间的关系,是复变函数的基础

Euler's formula, named after Leonhard Euler, is a mathematical formula in complex analysis that establishes the fundamental relationship between the trigonometric functions and the complex exponential function. Euler's formula states that for any real number x

eix = cos(x) + i*sin(x)

欧拉恒等式(Euler's Identity)e + 1 = 0 是 Euler's formula 当 x = π 时候的特殊情况

虽然这个等式被称为欧拉恒等式,但是应该是 Roger Cotes 首先发现的:

It has been claimed that Euler's identity appears in his monumental work of mathematical analysis published in 1748, Introductio in analysin infinitorum. However, it is questionable whether this particular concept can be attributed to Euler himself, as he may never have expressed it. (Moreover, while Euler did write in the Introductio about what we today call Euler's formula, which relates e with cosine and sine terms in the field of complex numbers, the English mathematician Roger Cotes (who died in 1716, when Euler was only 9 years old) also knew of this formula and Euler may have acquired the knowledge through his Swiss compatriot Johann Bernoulli.)

直观理解

欧拉公式之所以能建立三角函数和复平面指数函数之间的联系,是利用了复平面圆弧长度和三角函数圆弧长度之间的等值关系

摘自:
https://www.matongxue.com/madocs/8.html

三角函数的表示 指数函数的表示

欧拉恒等式的直观理解:

欧拉恒等式

Mathologer 的两个讲解:
https://www.youtube.com/watch?v=Yi3bT-82O5s
https://www.youtube.com/watch?v=-dhHrg-KbJ0

3Blue1Brown 的两个讲解:
https://www.youtube.com/watch?v=F_0yfvm0UoU
https://www.youtube.com/watch?v=mvmuCPvRoWQ(通过群论来理解)

对 复数的乘法、复数的平方、ex 的直观理解(圆心可以是平面卷曲以后最远的那个点,简直美哭了):
https://www.youtube.com/watch?v=1rVHLZm5Aho

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