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=z−1z+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.

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