The formula of polygon area Now we know the opposite sides and the number of sides of a regular polygon, such as 8, 12, 16, 20, 24, etc What does "a" on the second floor stand for

More questions, limited mobile code, talk about ideas For a regular polygon, find the central symmetric point O, connect one point X of the polygon with O, and draw a circle with ox as the radius. All the vertices of the regular polygon must be on the circle. The vertical line of XY crossing the center of the circle intersects XY with a, ax = XY / 2, and the angle of the center of the circle opposite to the edge ax is solvable. The height is obtained, and the area s is obtained. The total S = s * 2 * number of sides

Xiaohong, Xiaoli and Xiaoyu spent 23.75 yuan to the supermarket, Xiaoyu and Xiaoli spent 11.28 yuan, Xiaohong and Xiaoyu spent 13.15 yuan. How many yuan did Xiaohong, Xiaoli and Xiaoyu spend?

Xiaoyu 11.28 + 13.15-23.75 = 0.68 yuan
Xiaoli 11.28-0.68 = 10.6 yuan
Xiaohong 13.15-0.68 = 12.47 yuan
If you don't understand this question, you can ask,

On the national day, a total of 52 vehicles were inspected. Each vehicle was 4 meters long, and the distance between two adjacent vehicles was 6 meters. The motorcade drove 105 meters per minute. The motorcade had to pass the 536 meter long inspection site, and it had to pass the inspection site______ Minutes

The length of the motorcade is: 52 × 4 + (52-1) × 6, = 208 + 306, = 514 (m); the time required for the motorcade to pass the inspection site is: (514 + 536) △ 105, = 1050 △ 105, = 10 (min). A: it takes 10 minutes for the motorcade to pass the 536 m inspection site

80 points, 9 on the tenth, unknown on the individual, English: unknown on the tenth, 3 on each, average: 85
This classmate accidentally spilled ink on his final report card. Please help him calculate his Chinese and English scores
Ten minutes later, let's see if anyone answers

85x3 = 255 255-80 = 175 175-92 = 83 Chinese 92, English 83

1. 54 playing cards, Party A and Party B alternately draw cards, each one can only draw 1-4 cards at a time, who caught the last card to win. Ask how to let Party B win? 2, a pan can only bake 4 cakes, each 4 minutes (positive and negative each 2 minutes). How to bake 6 cakes only 6 minutes? The best formula

1）54/5=10…… two
Therefore, the number of the remaining cards should be added to that of a, which is equal to 5, that is, a grabs 1, B grabs 4; a grabs 2, B grabs 3
2) Put in 4 pieces first, take out 2 pieces after soldering one side, turn the other 2 pieces over, and then put in 2 new ones. It takes 2 minutes
After another 2 minutes, take out the 2 pieces, turn over the other 2 pieces, and then put in the original 2 pieces
After another 2 minutes, all the irons were finished

Mathematics problems in grade four of primary school
Mingming walks to school, each branch is 58 meters. 15 minutes after he goes out, his father finds that he has forgotten to bring his math book. His father immediately takes his math book with him and goes after him by bike. It is known that his father rides a bicycle 348 meters per minute. Can his father catch up with Mingming after a few minutes?
Please give some detailed and easy to understand explanation, so that I can understand. Thank you for your cooperation
Don't use equations to solve problems. I'm a senior in primary school. I don't know much about equations

Let dad catch up with Mingming in X minutes after departure. 348x = 58 * 15 + 58x

1. The circumference of a round piece of paper is 25.12 cm. How many cm is the circumference of the remaining part after subtracting half of the diameter?
2. The volume of cube is 12 cubic meters. Dig the largest cylinder inside and find the volume of the cylinder

1: 8 + 12.56 = 20.56 (diameter 8cm)
2: V = 12 * (Π / 4) = 3 Π (if Π is 3.14, then v = 9.42 m3)

1. The number of people in a class counted at one time is one ninth of the attendants. In the middle of the class, another person asks for leave to leave. In this way, the number of people asking for leave is three twenty-two percent of the attendants. How many people are there in this class?
2. A runs 14 kilometers per hour, B runs 11 kilometers per hour, B runs 10 minutes more than a, the result runs 1 kilometer less than a, ask B how many kilometers

1. There are 50 students in this class. Analysis: the dummy is one ninth of the attendants, the one who asks for leave and the nine who attend. Then there are 10 students in the class, and the dummy is one tenth of the class. In the middle of the class, there is another one who asks for leave. In this way, the number of people who ask for leave is three twenty-two of the attendants. At this time, the three who ask for leave and the three who attend

I don't understand the meaning of a math problem
I have a math problem that I don't understand. You can help me to have a look. If your meaning makes me understand, I will appreciate it. Title: use a 22 meter long fence to form a rectangular vegetable field, and use the house wall at the same time. What's the area of this vegetable field? The tip for you is: 6 meters wide, one side long into a wall

Sub situation:
1. Length as wall, length: 10; width: 6
Area: 60
2. Width as wall: length: 8; width: 6
Area: 48

A math problem I can't understand!
Why is the proposition that x belongs to R, 1 / x = 0 right? If the denominator cannot be zero, what number can be zero

The answer is correct. For x = 0, the value of 1 / X is the limit value, infinity, that is, when the denominator equals zero, the fraction is not zero
1 / x = 0, that is, when x is positive infinity, then Lim1 / x = 0 (that is, the limit of X is 0, that is, 1 / x = 0)

The formula of polygon area Now we know the opposite sides and the number of sides of a regular polygon, such as 8, 12, 16, 20, 24, etc What does "a" on the second floor stand for