Riemannian Geometry

Okay, let's start from what is Riemannian Geometry. It is simply Geometry on curved plane or what commonly called eliptical geometry.

Just look at the picture. In the positive curvature, the sum of the angles is > 180 degree or where is the Goddamn pi π and it is smaller when it is in saddle shaped curvature.

Need a better picture? I'll get them later.