through a point outside a given line, only one line can be drawn parallel to the given line
through a point outside a given line, only one line can be drawn parallel to the given line
through a point outside a given line, only one line can be drawn parallel to the given line <=> Euclidean space
through a point outside a given line, only one line can be drawn parallel to the given line
Riemannian space <=> elliptic space
through a point outside a given line, only one line can be drawn parallel to the given line
the sum of the angles of a triangle is always less than 180 degrees <=> hyperbolic space