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I. Understanding of Cylinders
1. Many objects in life are cylindrical, such as tea barrels, candles and cans. 2. Features of the cylinder: The cylinder is surrounded by three faces. Its upper and lower circular surfaces are called the bottom surface. The surface around the cylinder (except the upper and lower bottom surfaces) is called the side surface. Circle |? At the bottom, the height of the cylinder is parallel. The distance between the two bottom surfaces of a quadrangular prism is called height, and a cylinder has countless heights.
3. The top surface and bottom surface of a cylinder are two identical circles. The side of the cylinder is a curved surface, and it is a rectangle (or square) after being expanded along the height. The length (or side length) of this rectangle (or square) is equal to the circumference of the bottom of the cylinder, and the width (or side length) is equal to the height of the cylinder.
4. Stick a rectangular piece of hard paper on the stick and rotate the stick quickly. The figure formed by this rectangular piece of cardboard is a cylinder.
Second, the surface area of the cylinder
1. Side area of cylinder = perimeter x height of bottom surface, expressed in letters: Sw=Ch. If the diameter of the bottom surface is known, the formula for calculating the perimeter of the bottom surface is Cr π d.
2. Surface area of cylinder = side area+bottom area x2.
Third, the volume of the cylinder
1. The space occupied by a cylinder is called the volume of the cylinder.
2. The derivation process of cylinder volume is to divide the cylinder bottom into several parts along the radius.
Make an equal sector, treat the height of the cylinder according to the bisector, and cut them to make them soluble? Thinking method. Form an approximate cuboid. The more divided sectors, the closer the three-dimensional figure is to the cuboid. Spliced cuboids and cylinders have different shapes and equal volumes.