English translation

My best friend is Xiao Li, but last week, we had a big fight in school, she didn't talk to me. It's all because she asked me if she could copy my homework. I asked her why she did it, she said because she forgot to do it. I said I don't think it's a good idea for her to copy my homework

Translation on page 8 of English volume 2 of Grade 8

Do you think you will have your own robot?
In some science fiction movies, People in the future all have their own robots. These robots are just like human beings. They help people do housework and most boring jobs. Some scientists believe that there will be such robots in the future. However, it will take hundreds of years for them to come true. Scientists are trying to develop machines that look like human beings and can do the same work as us People. Some Japanese companies have made robots that can walk and dance. This kind of robot looks very interesting
But robot scientist James White doesn't agree with this view. He thinks it's very difficult for a robot to do things like human beings. For example, it's very easy for a child to wake up and know where he is. White thinks that robots can't do this. But other scientists don't agree. They think that in the next 25 to 30 years, Robots can talk to humans
Scientists who study robots are not just trying to make robots look like humans. For example, there are already robots that can work in factories. These robots look like giant arms. They can do simple work over and over again. Humans don't like doing this kind of work and are easily bored with it. But robots never get bored
In the future, there will be more robots everywhere, and less work for human beings. New robots will have many different shapes. Some look like human beings, others may look like snakes. After an earthquake, a snake like robot can help find people buried under buildings, Space rockets and even electric toothbrushes are considered impossible. We will never know what will happen in the future!

If a cylinder is cut 2 cm in height, its surface area will be reduced by 12.56 square cm~
If a cylinder cuts off its height by 2 cm, its surface area will be reduced by 12.56 square cm. What is its volume in cubic cm?

If the height is cut off by 2cm, the surface area will be reduced by 12.56cm, and the reduced area = the perimeter of the bottom surface × 2
Then the radius of the bottom surface is: 12.56 △ 2 (2 × 3.14) = 1
The volume of the cut off part is 3.14 × 1 & # 178; × 2 = 6.28cm & # 179;

How long does it take for the sun to reach the earth's surface?

Distance from the earth to the sun △ speed of light = time
In different seasons, the distance between the earth and the sun is not equal. We know that the trajectory of the earth is an ellipse, and the sun is at a focus of the ellipse. If we do not consider the influence of the atmosphere, it is generally considered to be 500 seconds, that is, 8 minutes and 20 seconds!

Calculation of chemical equation
A 6G iron nail is immersed in sufficient copper sulfate solution CuSO4 to react for a period of time, then it is taken out and dried to weigh 6.8g. Q. what is the mass of iron participating in the reaction? Why

Let the mass of iron in the reaction be XG
Fe+Cuso4==Cu+Feso4
56 64
(6.8-6)/(64-56)=x/56
x=5.6
A: the mass of iron in the reaction is 5.6g

There are two squares, one big and the other small, whose perimeter differs by 20 cm and area by 55 square cm. What is the area of a small square?
Use the primary school method to solve the problem

∵ the difference between the circumference of two squares is 20cm,
The difference between the sides of two squares is 5cm,
If the side length of the smaller square is xcm, the side length of the larger square is (x + 5) cm,
（x+5）²-x²=55,
The solution is x = 3,
∴x+5=8．
The area of small square = 9

Half plus six, one plus 12, one plus 20, one plus 30, one plus 42, one plus 50

One half plus one sixth plus one twelfth plus one twentieth plus one thirty plus one forty-two plus one fifty-six
=1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8
=1-1/8
=7/8
If you understand and solve your problem,

Cos (α - π) divided by sin (π minus α) multiplied by sin (α - 2 π) multiplied by cos (2 π - α)

cos（α-π）÷sin（π-α）×sin（α-2π）×cos（2π-α）
=cos（π-α）÷sin（π-α）×sin（α-2π）×cos（2π-α）
=(-cosα）÷sinα×sinα×cosα
=(-cosα）×cosα
=-(cosα)^2

The perimeter of a rectangle is 24. Now increase the length and width by 3, and the perimeter becomes 36
Use binary linear equation to solve

The length and width are increased by 3, the perimeter is increased by 3x4 = 12, 36-24 = 12, there are countless rectangles with perimeter of 24, so the area can not be calculated

The following ratio is 1:0.25, 9:16:4, 39:91

1：0.25
=1：1/4
=1÷1/4
=1×4
=4
9/16：3/4
=9/16÷3/4
=9/16×4/3
=3/4
39：91
=(39÷13)：(91÷13)
=3：7
=3/7

English translation