If you draw straight lines connecting those cities to make a triangle on the surface of the globe, you will find that the interior angles of that triangle add up to more than 180 degrees.

The three angles of a plane Euclidean triangle add to two right angles or 180 degrees. A triangle on the globe has three angles whose sum exceeds two right angles.

Everyone learns the number one rule about triangles in high school: the angles of a triangle add up to 180 degrees. But did you know that sometimes they don't? Triangles are much more interesting ...

A triangle inscribed on the surface of a sphere — a spherical geometric space — has more than 180 degrees in its internal angles, and one drawn on a saddle-shaped surface — a hyperbolic ...

Learn about angles in triangles and quadrilaterals with this BBC Bitesize Maths article. For students between the ages of 11 and 14.