Saccheri Quadrilaterals in the Half-plane Model

Saccheri Quadrilaterals This is an example in the half-plane model for hyperbolic geometry that demonstrates that a Saccheri quadrilateral need not be a rectangle. (A Saccheri quadrilateral is constructed by constructing perpendiculars at the endpoints of a base segment (EF), then laying off equal distances on the same side of the line containing that segment (distances s=t to make points K and L), then connecting the points (KL) to make a quadrilateral.)