Paper 1, Section I, F

Geometry
Part IB, 2015

(i) Give a model for the hyperbolic plane. In this choice of model, describe hyperbolic lines.

Show that if 1,2\ell_{1}, \ell_{2} are two hyperbolic lines and p11,p22p_{1} \in \ell_{1}, p_{2} \in \ell_{2} are points, then there exists an isometry gg of the hyperbolic plane such that g(1)=2g\left(\ell_{1}\right)=\ell_{2} and g(p1)=p2g\left(p_{1}\right)=p_{2}.

(ii) Let TT be a triangle in the hyperbolic plane with angles 30,3030^{\circ}, 30^{\circ} and 4545^{\circ}. What is the area of TT ?