# Möbius transformation

• Dec 3rd 2011, 01:12 PM
Homing
Möbius transformation
Consider the Möbiustransformation $\displaystyle w=z^2.$ Find the image, by this transformation of:

b) The region bounded by $\displaystyle x=1,$ $\displaystyle y=1$ and $\displaystyle x+y=1.$

What I have:

$\displaystyle w=z^2=(x+iy)^2=x^2-y^2+2ixy,$ so let $\displaystyle f(z)=f(x+iy)=x^2-y^2+2ixy,$ but now I don't know what's next. At least for part a) I have $\displaystyle x,y\ge0$ and for part b) I have a triangle with vertices $\displaystyle (0,0), (0,1)$ and $\displaystyle (1,0),$ but I don't know how to solve the problem though.

Any help appreciated!!
• Dec 4th 2011, 04:37 AM
Homing
Re: Möbius transformation
Can anybody help please? :(
• Dec 4th 2011, 05:09 AM
FernandoRevilla
Re: Möbius transformation
Hint Write the transformation in the form $\displaystyle \begin{Bmatrix} u=x^2-y^2\\v=2xy\end{matrix}$ and find previously the image of the boundaries.
• Dec 4th 2011, 11:59 AM
Homing
Re: Möbius transformation
You mean writing $\displaystyle w(x+iy)=u+vi$ ? For part a) I have $\displaystyle w(0)=0,$ but for part b) I have a triangle, it's just like putting the coordinates on $\displaystyle w$ ? I still don't get how to solve the problem. :(