In the picture below, we have two parallel and distinct planes,, a circle **R** contained in and a straight **r** that intercepts , but not **R**:

For each point **Ç** Of region **R**, let's consider the segment , parallel to the straight line **r :**

Thus we have:

We call it *cylinder, or circular cylinder, *the set of all segments congruent and parallel to **r**.

## Cylinder Elements

Given the following cylinder, consider the following elements:

bases: the center circles

**O**and**O'**and lightning**r**height: the distance

**H**between the plansgeneratrix: any end segment at the points of the base circumferences (for example, ) and parallel to the straight

**r**

## Cylinder Classification

A cylinder can be:

oblique circular: when the generatrices are oblique to the bases;

straight circular: when the geratrices are perpendicular to the bases.

Look:

The straight circular cylinder is also called the revolution cylinder because it is generated by the complete rotation of a rectangle on one side. Thus, the rotation of the ABCD rectangle by the side generates the following cylinder:

The straight contains the centers of the bases and is the axis of the cylinder.

Next: Cylinder Sections