How to extract a certain number of matrix in MATLAB RT For example, a = 1 two How to extract 1 is to let I =

How to extract a certain number of matrix in MATLAB RT For example, a = 1 two How to extract 1 is to let I =

If a = [1; 2], it means that the column matrix A (1,1) = 1, a (2,1) = 2
If a = [1,2], it means row matrix A (1,1) = 1, a (2,1) = 2
A (m, n) is also used to identify multi row and multi column. M represents the number of rows and N represents the number of columns

How to get the condition number of a matrix A in MATLAB

c = cond(A,p)
The second parameter is the condition number of several normal forms
If it is not written, it defaults to the second normal form

The negative 5th power of 7 × 10 = () um

0.7

In order to catch the train, Mr. Li had to arrive at the railway station at the appointed time. If he started from home and walked 3 kilometers per hour, he would be 20 minutes late than the scheduled time
So he walked an extra kilometer per hour and arrived at the railway station 40 minutes earlier than the scheduled time?

The distance from home to railway station is x km
have to
x/3+1/3=x/4-2/3
X = 12 km

As shown in the figure, Xiao Hong cuts a 4 cm wide strip from a square, and then cuts a 5 cm wide strip from the remaining rectangular paper along the direction parallel to the short side. If the area of the strips cut twice is exactly the same, what is the area of each strip? What is the area of the original square?

Suppose the side length of the square is xcm, then according to the meaning of the question: 4x = 5 (x-4), the solution is: x = 20. Then 4x = 80 (cm2), 20 × 20 = 400 (cm2). Answer: the area of each strip is 80cm2, the area of the original square is 400cm2

In △ ABC, a + C = 2B, and the ratio of the opposite length of the largest angle to the smallest angle is (3 + 1): 2. Find the size of a, B, C

Because in △ ABC, a + C = 2B, so 180 ° = a + B + C = 3b, then B = 60 ° (2) if the maximum angle is a, the minimum angle is C (3 points) because the ratio of the length of the opposite side of the maximum angle to the minimum angle is (3 + 1): 2, according to the sine theorem, 3 + 12 = sinasinc = sin (120 ° − C) sinc = 32cosc + 12sincsinc = 32cotc + 12 So COTC = 1 (12 points) because C is the internal angle of a triangle, C = 45 degree So a = 75 degree If the maximum angle is C and the minimum angle is a, then a = 45 ° and C = 75 ° In conclusion, a = 75 °, B = 60 °, C = 45 ° or a = 45 °, B = 60 ° C = 75 ° (16 points)

A project, team a need to do 10 days to complete, team B need to do 20 days to complete, the two teams work together to pull three days, team a adopts new technology, work efficiency increased by 1 / 3, ask team a to adopt new technology, the two teams need to cooperate how many days to complete the project

Solution 1: team a needs to do 10 days to complete, 1 / 10 of the total amount per day, team B needs to do 20 days to complete, 1 / 20 of the total amount per day, the two teams work together to pull for 3 days, a total of 3 * (1 / 10 + 1 / 20) of the total amount per day, the remaining 1-3 * (1 / 10 + 1 / 20) = 11 / 20

Cut a piece of paper with a side length of 10 cm into the largest circle. What percentage of the area of the circle is that of the square?

The area of the circle: S = π R2 = 3.14 × (10 △ 2) 2 = 78.5 (square centimeter); the area of the square: S = A2 = 10 × 10 = 100 (square centimeter); 78.5 △ 100 = 78.5%; answer: the area of the circle is 78.5% of the area of the square

In RT △ ABC, angle c = 90 °, ad bisects ∠ BAC, and ad = BD

Making DH ⊥ AB through D and crossing AB with H
∵AD=AB
‖ angle Dah = angle DBH
∵DH⊥AB
｜ ah = half ab
∵ angle CAD = angle had
Angle c = angle ahd
∴AC=AH
｜ AC = half ab

Proportion problem,
1. A new type of beverage is made of mineral water, fruit juice and milk in the ratio of 5:3:2. If all the three drinks have 2 liters, when all the fruit juice is used up, how much milk is left, and how much mineral water has been added in the production?
2. Five tons of cement, yellow sand and stones are transported from the construction site, and they are made into a kind of concrete according to the ratio of 2:3:5. If the yellow sand is to be used up, how many tons of stones are needed?

1. If 2 liters of juice is used, 2 * 5 / 3 = 10 / 3 raw mineral water is needed, so 10 / 3-2 = 4 / 3 liter mineral water is added
2 * 2 / 3 = 4 / 3 liters of milk is used, and 2-4 / 3 = 2 / 3 liters are left
There are still 2 / 3 liters of milk left and 4 / 3 liters of mineral water added
2. When the yellow sand is completely used up, it needs 5 * 5 / 3 = 25 / 3 tons of stones, and it also needs 25 / 3-5 = 10 / 3 tons
We need 10 / 3 tons of stones