1. Cut the cylinder along the height to get a rectangle. When the perimeter of the bottom surface is not equal to the height, the side development diagram is rectangular, and when the perimeter of the bottom surface is equal to the height, the side development diagram is square. Cut the cylinder along the straight line (except the height) on the side, and the side development diagram is a parallelogram.

2. If the cylinder is unfolded to get a rectangle, the length of the rectangle is equal to the circumference of the bottom circle of the cylinder, and the width is equal to the height of the cylinder.

3. When the circumference and height of the cylinder bottom are equal, expand it into a square. Because it is a rectangle, and the length = width of a rectangle is a square.

4. The radius of the bottom surface of the cylinder is 2cm and the height is 4cm. The length of the rectangle obtained by side expansion is =

2πr=2×2×π= 12.56 (cm)。 The width is 4 cm. The width is the height of the cylinder.

5. The height of the cylinder is10cm. How to calculate its bottom perimeter and radius? Unable to calculate, the height has nothing to do with the radius of the bottom surface.

6. Take a closer look at the first and second points I said, and the surface area and volume of the cylinder will be fine. I can't beat you. Let's go