Paper 1, Section I, A

Complex Analysis or Complex Methods
Part IB, 2018

(a) Show that

w=log(z)w=\log (z)

is a conformal mapping from the right half zz-plane, Re(z)>0\operatorname{Re}(z)>0, to the strip

S={w:π2<Im(w)<π2}S=\left\{w:-\frac{\pi}{2}<\operatorname{Im}(w)<\frac{\pi}{2}\right\}

for a suitably chosen branch of log(z)\log (z) that you should specify.

(b) Show that

w=z1z+1w=\frac{z-1}{z+1}

is a conformal mapping from the right half zz-plane, Re(z)>0\operatorname{Re}(z)>0, to the unit disc

D={w:w<1}D=\{w:|w|<1\}

(c) Deduce a conformal mapping from the strip SS to the disc DD.