Surfaces of revolution and solids of revolution.

Move the red dot very slowly to the right.
Thus, the segments and semi-circumference of the figure will rotate 360º, each figure around its own axis.
And so, three surfaces of revolution will form: cylindrical surface, conical surface and spherical surface.
The line that makes the rotation in the cylindrical surface and the conical surface is known as generatrix.

If, instead of lines, we rotate:
- a rectangle with a side as its axis,
- a right-angled triangle with an edge as its axis,
- and a semicircle with the diameter as its axis,
...we get a cylinder, a cone and a sphere respectively.

The cylinder, the cone and the sphere are the best known solids of revolution.