1. Collect a cylindrical object and take photos, as shown in the following figure1;

Second, cut a piece of paper with the right size, so that the paper is not too much, too little, too high or too short, just enough to surround the two sides of the column, and then take pictures after it is surrounded, as shown in Figure 2 or 3 below.

Third, submit two photos to nail the operation.

1. Side expansion diagram operation:

Fill in the blanks.

Cut the side along the height of the cylinder. The side development diagram is generally rectangular, the length of the rectangle is cylindrical (), and the width of the rectangle is cylindrical ().

When () and () of a cylinder are equal, its side-view development diagram is square.

If it is cut along the diagonal of the cylinder side, the side expansion diagram is a parallelogram, the length of the parallelogram is a cylinder (), and the height of the parallelogram is a cylinder ().

Second, correct the answers by yourself, then recite the content and send the recited voice to the "recording" in Tintin's homework.

Cut the side along the height of the cylinder. The side development diagram is generally rectangular, and the length of the rectangle is cylinder (? The perimeter of the bottom), the width of the rectangle is the height of the cylinder.

When the (bottom circumference) and (height) of a cylinder are equal, its side development diagram is square.

If cut along the diagonal of the cylinder side, the side expansion diagram is a parallelogram, the length of the parallelogram is the cylinder (the perimeter of the bottom), and the height of the parallelogram is the cylinder (the height).

Third, solve the problem.

1.？ The diameter of the bottom surface of the cylinder is 5cm and the height is15.7cm.. Find the length and width of its side expansion diagram.

2.？ The radius of the bottom surface of the cylinder is 1.5 cm, and its side development diagram is square. Find the height of this cylinder.

3.？ A cylinder with a height of 2 1.98 cm. Its side development diagram is square. Find the radius of the bottom of this cylinder.

Fill in the blanks.

A rectangle with a length of 7 cm and a width of 4 cm can be rotated around its side to get two cylinders.

(1) If you rotate around a 7 cm edge,

The radius of the bottom of the cylinder is () cm and the height is (? ) centimeters.

(2) If you rotate around a 4 cm edge,

The radius of the bottom of the cylinder is () cm and the height is (? ) centimeters.

Tip: If you can't figure it out, just cut a rectangle and mark it with 7 and 4. Turn around and think about it before filling it out.

2. Transverse area, surface area operation:

fill (up) a vacancy

(1) A rectangle with a length of 5 cm and a width of 4 cm is a cylinder rotating around its long side of 5 cm, with a height of () cm and a bottom radius of (? ) cm, the bottom circumference is () cm; What is the height of the cylinder rotating around the axis with a short side of 4 cm? ) cm, the bottom radius is () cm and the bottom circumference is () cm. Tip: If you don't fill in my live topic before 8: 30 this morning.

(2) The lateral area of a cylinder refers to the lateral area of the cylinder.

Cut the side along the height of the cylinder. The side development diagram is generally rectangular, the length of the rectangle is cylindrical (), and the width of the rectangle is cylindrical ().

Therefore, to find the lateral area of a cylinder, it is actually required that the area of a rectangle is equal to the length and width, that is, it is represented by () () of the cylinder, and it is represented by a symbol, that is, lateral area = ch.

Second, solve the problem.

Find the transverse areas of the following two cylinders:

(1) A cylinder with a base diameter of 5cm and a height of 3cm.

(2) A cylinder with a bottom radius of 8 decimeters and a height of 8 decimeters.

Three, the surface area of the cylinder refers to (? )。 For example, the radius of the bottom of the cylinder is 2 cm and the height is 5 cm. (Write the formula in the brackets below to find the result)

The transverse area is (? )。 The bottom area is (? )。 What is the surface area? )。 Imitate the above example and find the surface area of the cylinder below in three steps.

The diameter of the bottom surface is 6m, and the height is 10m (again: divided into three steps).

Two attempts to organize and review;

First of all, mind mapping

Second, the voice homework

You don't need to do this homework. Click on the recording in the Tintin group. Do not look at the original question. Just answer the following five questions orally and submit them (the questions can be sent to you in screenshots, which is more convenient for students to see the questions in the pictures).

1. What does cylindrical lateral area mean? What is the calculation formula? How is it derived?

2. What is the surface area of the cylinder? How to find the surface area of a cylinder? What should I pay attention to?

3. When calculating the surface area of cylindrical objects in real life, which objects have only one bottom surface and one side surface? What object has no bottom and only edges?

4. How many knives does it take to cut a cylindrical piece of wood into two parts? How many more faces will there be than before?

Cut it into three parts?

Cut it into four sections?

What is the relationship between the number of knives to be cut and the number of segments to be cut?

What is the relationship between the number of extra noodles and the number of knives?