Two identical circular surfaces of a cylinder are called the bottom surface (divided into upper bottom surface and lower bottom surface); A cylinder has a curved surface called a side surface; The distance between the corresponding points of two bottom surfaces is called height (there are countless heights).

Features:

1, the bottom of the cylinder is round and the size is the same.

2. The vertical distance between two sides of a cylinder is called height. Open one side of the cylinder and get a rectangle. The length of this rectangle is the circumference of the bottom of the cylinder.

Second, the area calculation

Transverse area of cylinder = bottom circumference × height.

S side =2πrh=πdh

The bottom area of a cylinder =πr?

Surface area of cylinder

Surface area of cylinder = side area+two bottom areas (S table =s side +2s bottom).

S table =2πr? +2πrh =2πr？ +πdh

Third, the definition of cylinder

1, with rectangle

One side of the straight line is the axis of rotation, and the geometry surrounded by the curved surface formed by the other three sides rotating 360 degrees is called a cylinder, that is, one side of the AG rectangle is the axis, and the geometry obtained by rotating 360 degrees is a cylinder. Among them, AG is called the axis of the cylinder, the length of AG is called the height of the cylinder, and the side not perpendicular to the axis is called the generatrix of the cylinder wherever it rotates. The two circles formed by the rotation of DA and D'G are called the bottom surface of the cylinder, and the curved surface formed by the rotation of d' d is called the side surface of the cylinder.

2. There is a fixed line and a moving line in the same plane. When the plane rotates once around this fixed line, the surface formed by this moving line is called the rotating surface, this fixed line is called the axis of the rotating surface, and this moving line is called the generatrix of the rotating surface. If the generatrix is a straight line parallel to the axis, then the generated surface of revolution is called a cylindrical surface. If two planes perpendicular to the axis are used to cut the cylindrical surface, then the geometry surrounded by these two sections and the cylindrical surface is called a straight cylinder, which is called cylinder for short.