Paper 1, Section I, F

Geometry
Part IB, 2011

Suppose that HCH \subseteq \mathbb{C} is the upper half-plane, H={x+iyx,yR,y>0}H=\{x+i y \mid x, y \in \mathbb{R}, y>0\}. Using the Riemannian metric ds2=dx2+dy2y2d s^{2}=\frac{d x^{2}+d y^{2}}{y^{2}}, define the length of a curve γ\gamma and the area of a region Ω\Omega in HH.

Find the area of

Ω={x+iyx12,x2+y21}\Omega=\left\{x+i y|| x \mid \leqslant \frac{1}{2}, x^{2}+y^{2} \geqslant 1\right\}