The base and summit of a Saccheri quadrilateral are divergently parallel, as are the other two sides. The summit angles of every Saccheri quadrilateral are acute. The angle-sum of every triangle is less than 180 . If the three angles of one triangle are equal, respectively, to the three angles of another triangle, then the triangles are congruent. Two divergent parallels have a unique common perpendicular.
Divergent parallels veer away from each other on either side of their common perpendicular.
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