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Math diary 450 words
Today, I previewed the lesson "Cylinders", which gave me a deeper understanding of cylinders. I know the names of the parts of the cylinder, and I can draw some cylinders. Through observation, I found that the upper bottom and the lower bottom of the cylinder are exactly the same two circles. After I cut the side of the cylinder along a height, I found that it is a rectangle. The length of this rectangle is the circumference of the bottom of the cylinder, the width of the rectangle is the height of the cylinder, and the area of the rectangle is the side area of the cylinder. From this, I get the lateral area of a cylinder = the circumference of the bottom × the height. I have gained a lot in this course. I am very happy! Today we are going to learn "the volume of a cylinder", because I have long known that the formula for calculating the volume of a cylinder is the bottom area multiplied by the height, so I am not interested in this lesson at all and think it is too easy. I didn't pay much attention to the lecture at first. When the teacher took out the cylindrical teaching aid and asked, "How can I deduce the cylindrical volume formula?" I was puzzled and began to use my head. During the group discussion, I was a little anxious to see that math was not as good as my classmates had quickly figured out the relationship between cuboids and cubes. Ask the students how they came up with it. They said that the teacher had just reviewed the derivation of the area formula of a circle and the volume formula of a cuboid, and they knew what was going on as soon as they touched it. It's simple. I just don't listen. Just combine.