From 6d4b8f8ca40cb859f7ddd63f54a6febd808ffb95 Mon Sep 17 00:00:00 2001 From: Trance-0 <60459821+Trance-0@users.noreply.github.com> Date: Wed, 12 Mar 2025 20:40:18 -0500 Subject: [PATCH] Update Math416_E1.md --- pages/Math416/Exam_reviews/Math416_E1.md | 333 ++++++++++++++++++++++- 1 file changed, 330 insertions(+), 3 deletions(-) diff --git a/pages/Math416/Exam_reviews/Math416_E1.md b/pages/Math416/Exam_reviews/Math416_E1.md index 4d2f64d..653d5ad 100644 --- a/pages/Math416/Exam_reviews/Math416_E1.md +++ b/pages/Math416/Exam_reviews/Math416_E1.md @@ -2,6 +2,213 @@ So everything we have learned so far is to extend the real line to the complex plane. +## Chapter 0 Calculus on Real values + +### Differentiation + +Let $f,g$ be function on real line and $c$ be a real number. + +$$ +\frac{d}{dx}(f+g)=f'+g' +$$ + +$$ +\frac{d}{dx}(cf)=cf' +$$ + +$$ +\frac{d}{dx}(fg)=f'g+fg' +$$ + +$$ +\frac{d}{dx}(f/g)=(f'g-fg')/g^2 +$$ + +$$ +\frac{d}{dx}(f\circ g)=(f'\circ g)\frac{d}{dx}g +$$ + +$$ +\frac{d}{dx}x^n=nx^{n-1} +$$ + +$$ +\frac{d}{dx}e^x=e^x +$$ + +$$ +\frac{d}{dx}\ln x=\frac{1}{x} +$$ + +$$ +\frac{d}{dx}\sin x=\cos x +$$ + +$$ +\frac{d}{dx}\cos x=-\sin x +$$ + +$$ +\frac{d}{dx}\tan x=\sec^2 x +$$ + +$$ +\frac{d}{dx}\sec x=\sec x\tan x +$$ + +$$ +\frac{d}{dx}\csc x=-\csc x\cot x +$$ + +$$ +\frac{d}{dx}\sinh x=\cosh x +$$ + +$$ +\frac{d}{dx}\cosh x=\sinh x +$$ + +$$ +\frac{d}{dx}\tanh x=\operatorname{sech}^2 x +$$ + +$$ +\frac{d}{dx}\operatorname{sech} x=-\operatorname{sech}x\tanh x +$$ + +$$ +\frac{d}{dx}\operatorname{csch} x=-\operatorname{csch}x\coth x +$$ + +$$ +\frac{d}{dx}\coth x=-\operatorname{csch}^2 x +$$ + +$$ +\frac{d}{dx}\arcsin x=\frac{1}{\sqrt{1-x^2}} +$$ + +$$ +\frac{d}{dx}\arccos x=-\frac{1}{\sqrt{1-x^2}} +$$ + +$$ +\frac{d}{dx}\arctan x=\frac{1}{1+x^2} +$$ + +$$ +\frac{d}{dx}\operatorname{arccot} x=-\frac{1}{1+x^2} +$$ + +$$ +\frac{d}{dx}\operatorname{arcsec} x=\frac{1}{x\sqrt{x^2-1}} +$$ + +$$ +\frac{d}{dx}\operatorname{arccsc} x=-\frac{1}{x\sqrt{x^2-1}} +$$ + +### Integration + +Let $f,g$ be function on real line and $c$ be a real number. + +$$ +\int (f+g)dx=\int fdx+\int gdx +$$ + +$$ +\int cfdx=c\int fdx +$$ + +$$ +\int e^x dx=e^x +$$ + +$$ +\int \ln x dx=x\ln x-x +$$ + +$$ +\int \frac{1}{x} dx=\ln|x| +$$ + +$$ +\int \sin x dx=-\cos x +$$ + +$$ +\int \cos x dx=\sin x +$$ + +$$ +\int \tan x dx=-\ln|\cos x| +$$ + +$$ +\int \cot x dx=\ln|\sin x| +$$ + +$$ +\int \sec x dx=\ln|\sec x+\tan x| +$$ + +$$ +\int \csc x dx=\ln|\csc x-\cot x| +$$ + +$$ +\int \sinh x dx=\cosh x +$$ + +$$ +\int \cosh x dx=\sinh x +$$ + +$$ +\int \tanh x dx=\ln|\cosh x| +$$ + +$$ +\int \coth x dx=\ln|\sinh x| +$$ + +$$ +\int \operatorname{sech} x dx=2\arctan(\tanh(x/2)) +$$ + +$$ +\int \operatorname{csch} x dx=\ln|\coth x-\operatorname{csch} x| +$$ + +$$ +\int \operatorname{sech}^2 x dx=\tanh x +$$ + +$$ +\int \operatorname{csch}^2 x dx=-\coth x +$$ + +$$ +\int \frac{1}{1+x^2} dx=\arctan x +$$ + +$$ +\int \frac{1}{x^2+1} dx=\arctan x +$$ + +$$ +\int \frac{1}{x^2-1} dx=\frac{1}{2}\ln|\frac{x-1}{x+1}| +$$ + +$$ +\int \frac{1}{x^2-a^2} dx=\frac{1}{2a}\ln|\frac{x-a}{x+a}| +$$ + +$$ +\int \frac{1}{x^2+a^2} dx=\frac{1}{a}\arctan(\frac{x}{a}) +$$ + + ## Chapter 1 Complex Numbers ### Definition of complex numbers @@ -18,6 +225,14 @@ $$ (x_1 + y_1i) \cdot (x_2 + y_2i) = (x_1x_2 - y_1y_2) + (x_1y_2 + x_2y_1)i $$ +#### Modulus + +The modulus of a complex number $z = x + yi$ is defined as + +$$ +|z| = \sqrt{x^2 + y^2}=|z\overline{z}| +$$ + ### De Moivre's Formula Every complex number $z$ can be written as $z = r(\cos \theta + i \sin \theta)$, where $r$ is the magnitude of $z$ and $\theta$ is the argument of $z$. @@ -121,6 +336,12 @@ $$ \frac{\partial u}{\partial x} = \frac{\partial v}{\partial y}, \quad \frac{\partial u}{\partial y} = -\frac{\partial v}{\partial x} $$ +On the polar form, the Cauchy-Riemann equations are + +$$ +r\frac{\partial u}{\partial r} = \frac{\partial v}{\partial \theta}, \quad \frac{\partial u}{\partial \theta} = -r\frac{\partial v}{\partial r} +$$ + ### Holomorphic functions A function $f$ is said to be holomorphic on an open subset $G$ of $\mathbb{C}$ if $f$ is differentiable at every point of $G$. @@ -190,6 +411,21 @@ where $a,b,c,d$ are complex numbers and $ad-bc\neq 0$. ### Properties of linear fractional transformations +#### Matrix form + +A linear fractional transformation can be written as a matrix multiplication: + +$$ +\phi(z) = \begin{bmatrix} +a & b\\ +c & d\\ +\end{bmatrix} +\begin{bmatrix} +z\\ +1\\ +\end{bmatrix} +$$ + #### Conformality A linear fractional transformation is conformal. @@ -215,21 +451,99 @@ $$ So if $z_1,z_2,z_3$, $w_1,w_2,w_3$ are distinct points in the complex plane, then there exists a unique linear fractional transformation $\phi$ such that $\phi(z_i)=w_i$ for $i=1,2,3$. -#### Inversion - - #### Factorization +Every linear fractional transformation can be written as a composition of homothetic mappings, translations, inversions, and multiplications. + +If $\phi(z)=\frac{az+b}{cz+d}$, then + +$$ +\phi(z) = \frac{b-ad/c}{cz+d}+\frac{a}{c} +$$ + #### Clircle +A linear-fractional transformation maps circles and lines to circles and lines. + ## Chapter 4 Elementary Functions ### Exponential function +The exponential function is defined as + +$$ +e^z = \sum_{n=0}^\infty \frac{z^n}{n!} +$$ + +Let $z=x+iy$, then + +$$ +\begin{aligned} +e^z &= e^{x+iy}\\ +&= e^x e^{iy}\\ +&= e^x\sum_{n=0}^\infty \frac{(iy)^n}{n!}\\ +&= e^x\sum_{n=0}^\infty \frac{(-1)^n y^{2n}}{(2n)!} + i \sum_{n=0}^\infty \frac{(-1)^n y^{2n+1}}{(2n+1)!}\\ +&= e^x(\cos y + i\sin y)\\ +\end{aligned} +$$ + +So we can rewrite the polar form of a complex number as + +$$ +z = r(\cos \theta + i\sin \theta) = re^{i\theta} +$$ + +#### $e^x$ is holomorphic + +Let $f(z)=e^z$, then $u(x,y)=e^x\cos y$, $v(x,y)=e^x\sin y$. + +$$ +\frac{\partial u}{\partial x} = e^x\cos y = \frac{\partial v}{\partial y}\\ +\frac{\partial u}{\partial y} = -e^x\sin y = -\frac{\partial v}{\partial x} +$$ + ### Trigonometric functions +$$ +\sin z = \frac{e^{iz}-e^{-iz}}{2i}, \quad \cos z = \frac{e^{iz}+e^{-iz}}{2}, \quad \tan z = \frac{\sin z}{\cos z} +$$ + +$$ +\sec z = \frac{1}{\cos z}, \quad \csc z = \frac{1}{\sin z}, \quad \cot z = \frac{1}{\tan z} +$$ + +#### Hyperbolic functions + +$$ +\sinh z = \frac{e^z-e^{-z}}{2}, \quad \cosh z = \frac{e^z+e^{-z}}{2}, \quad \tanh z = \frac{\sinh z}{\cosh z} +$$ + +$$ +\operatorname{sech} z = \frac{1}{\cosh z}, \quad \operatorname{csch} z = \frac{1}{\sinh z}, \quad \operatorname{coth} z = \frac{1}{\tanh z} +$$ + ### Logarithmic function +The logarithmic function is defined as + +$$ +\ln z=\{w\in\mathbb{C}: e^w=z\} +$$ + +#### Properties of the logarithmic function + +Let $z=x+iy$, then + +$$ +|e^z|=\sqrt{e^x(\cos y)^2+(\sin y)^2}=e^x +$$ + +So we have + +$$ +\log z = \ln |z| + i\arg z +$$ + ### Power function ### Inverse trigonometric functions @@ -238,8 +552,21 @@ So if $z_1,z_2,z_3$, $w_1,w_2,w_3$ are distinct points in the complex plane, the ### Definition of power series +A power series is a series of the form + +$$ +\sum_{n=0}^\infty a_n (z-z_0)^n +$$ + ### Properties of power series +#### Geometric series + +$$ +\sum_{n=0}^\infty z^n = \frac{1}{1-z}, \quad |z|<1 +$$ + + ### Radius/Region of convergence ### Cauchy-Hadamard Theorem