复分析

作者: 烟流 | 来源:发表于2019-01-03 10:41 被阅读0次

week3

week3 -柯西-黎曼等式

如果函数fz出可微:
f(z) = u(x,y) + v(x,y)i
f_x^{'}(z)=u_x^{'}(x,y) + i v_x^{'}(x,y)
f_y^{'}(z)=u_y^{'}(x,y) + i v_y^{'}(x,y)
f^{'} = f_x^{'} = -if_y^{'}
u_x^{'} = v_y^{'} , u_y^{'} = -v_x^{'}

反之,如果不满足柯西-黎曼等式.则函数fz上不可微

Lesson 4 Trigonometric

e^{zi} = cos(z) + i sin(z)
e^{-zi} = cos(z) - i sin(z)

cos(z) = \frac{e^{zi}+e^{-zi}}{2}
sin(z) = \frac{e^{zi}-e^{-zi}}{2i}

week4

inverse function

if f(z) , g(z)=f^{-1}(z)

then g^{'}(z) = \frac{1}{f^{'}(g(z))}

coformal mapping

define : tangent of \gamma_1(t),\gamma_2(t) = f(\gamma_1(t),f(\gamma_2(t))

if f is coformal mapping then 它的导数处处非零

week 5

柯西定理

沿着封闭且联通的曲线\gamma 积分
\int f(z)dz = 0

如果在封闭的曲线\gamma_1 \gamma_2 内 存在 奇点
\int_{\gamma_1} f(z)dz = \int_{\gamma_2} f(z)dz

柯西积分公式

f^{(k)}(w)=\frac{k!}{2\pi i} \int_{\gamma} \frac{f(z)}{(z-w)^{k+1}} , w \in D , k >=0 , \gamma is close and contain w


留数定理,residues

\int_\gamma f(z) dz = 2\pi i \sum Res(f,奇点)

寻找留数

  • taylor(f) ; a\frac{1}{z}的系数a就是
  • Res(f,c) = \frac{g(c)}{h^{'}(c)}
  • Res(f,c) = \lim\limits_{z \to c}(z-c)f(c)
  • Res(f,c) = \lim\limits_{z \to c} \frac{d^{n-1}}{dz^{n-1}} (z-c)^n f(z)

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