Geometry Euclidean and Non-Euclidean Geometries Click here to go the the General Relativity page.
Geometry is the archetype of the beauty of the world.
If someone likes puzzles in logic, then various relations can be proved from the above statements. For example, it can be shown that the class K contains exactly 3 members. We can form a model that obeys the above five statements, and then logically all relations derived from the statements will also be true for the model. One such model is that K is the vertices of a triangle, and L is the sides of that triangle. All A are equal.