However, people from ancient astronomers to modern navigators calculated the arc lengths and angles of triangles on a sphere. They used special globes and instruments to make measurements and teach.

You can get pyramids with different shaped bases. Triangles, pentagons, hexagons, any shape. And a circle becomes a sphere with just one large, curved face, like a ball. Perfect for, uh ...

The square describes his world as a plane populated by lines, circles, squares, triangles ... which can see only a slice of the sphere, the shape before him is that of a two-dimensional circle.

When the cross-section is a triangle, the prism is called ... curved face made from a sector of a circle. A sphere is completely curved, a ball shape. Image caption, A cylinder has a constant ...