### Related items

#### Sphere

A sphere is the set of points which are all within the same distance from a given point in space.

#### Four colour theorem

Colour a map with the fewest number of colours possible, so that no two adjacent regions have the same colour.

#### Non-orientable surfaces

The Möbius strip and the Klein bottle are special two-dimensional surfaces with only one side.

#### Perimeter, area, surface area and volume

This animation presents the formulas to calculate the perimeter and area of shapes as well as the surface area and volume of solids.

#### Volume of spheres (Cavalieri´s principle)

Calculating the volume of a sphere is possible using an appropriate cylinder and cone.

#### Volume of spheres (demonstration)

The sum of the volume of the ´tetrahedrons´ gives an approximation of the volume of the sphere.

#### Geometric transformations – rotation

This animation demonstrates geometric rotation, a type of geometric transformation both in plane and space.

#### Solids of revolution

Rotating a geometric shape around a line within its geometric plane as an axis results in a solid of revolution.