diff --git a/pages/Math416/Math416_L5.md b/pages/Math416/Math416_L5.md index 29c7f00..be039b2 100644 --- a/pages/Math416/Math416_L5.md +++ b/pages/Math416/Math416_L5.md @@ -4,20 +4,24 @@ Let $f$ be a complex function. that maps $\mathbb{R}^2$ to $\mathbb{R}^2$. $f(x+iy)=u(x,y)+iv(x,y)$. -$Df(x+iy)=\begin{pmatrix} +$$ +Df(x+iy)=\begin{pmatrix} \frac{\partial u}{\partial x} & \frac{\partial u}{\partial y}\\ \frac{\partial v}{\partial x} & \frac{\partial v}{\partial y} \end{pmatrix}=\begin{pmatrix} \alpha & \beta\\ \sigma & \delta -\end{pmatrix}$ +\end{pmatrix} +$$ So -$$\begin{aligned} +$$ +\begin{aligned} \frac{\partial f}{\partial \zeta}&=\frac{1}{2}\left(u_x+v_y\right)-i\frac{1}{2}\left(v_x+u_y\right)\\ &=\frac{1}{2}\left(\alpha+\delta\right)-i\frac{1}{2}\left(\beta-\sigma\right)\\ -\end{aligned}$$ +\end{aligned} +$$ $$ \begin{aligned} @@ -26,19 +30,30 @@ $$ \end{aligned} $$ -When $f$ is conformal, $Df(x+iy)=\begin{pmatrix} +When $f$ is conformal, + +$$ +Df(x+iy)=\begin{pmatrix} \alpha & \beta\\ -\beta & \alpha -\end{pmatrix}$. +\end{pmatrix} +$$ -So $\frac{\partial f}{\partial \zeta}=\frac{1}{2}(\alpha+\alpha)+i\frac{1}{2}(\beta+\beta)=a$ +So, -$\frac{\partial f}{\partial \overline{\zeta}}=\frac{1}{2}(\alpha-\alpha)+i\frac{1}{2}(\beta-\beta)=0$ +$$ +\frac{\partial f}{\partial \zeta}=\frac{1}{2}(\alpha+\alpha)+i\frac{1}{2}(\beta+\beta)=a +$$ + +$$ +\frac{\partial f}{\partial \overline{\zeta}}=\frac{1}{2}(\alpha-\alpha)+i\frac{1}{2}(\beta-\beta)=0 +$$ > Less pain to represent a complex function using four real numbers. ## Chapter 3: Linear fractional Transformations + Let $a,b,c,d$ be complex numbers. such that $ad-bc\neq 0$. The linear fractional transformation is defined as