It is known that, as shown in the figure, D is a point on the edge of BC in △ ABC, e is a point on ad, EB = EC, ∠ Abe = ∠ ace, and verification: ∠ BAE = ∠ CAE

It is known that, as shown in the figure, D is a point on the edge of BC in △ ABC, e is a point on ad, EB = EC, ∠ Abe = ∠ ace, and verification: ∠ BAE = ∠ CAE

It is proved that: ∵ EB = EC, ∵ EBD = ECD, and ∵ Abe = ace, ∵ ABC = ACB, ∵ AB = AC, in △ Abe and △ ace, ab = aceb = ECAE = AE ≌ Abe ≌ ace, ≌ BAE = CAE

1 square meter 20 square decimeter =? Square decimeter

Because 1 square meter = 100 square decimeters
So 1 square meter 20 square decimeter = 120 square decimeter

The school playground is semicircular at both ends and rectangular in the middle. How many meters is it to run around the playground? How many square meters is the playground area
The rectangle is 100 meters, and the radius of the semicircle is 20 meters,

One circle is 20 * 2 * 3.14 + 100 * 2 = 325.6m
The playground area is: 20 * 20 * 3.14 + 100 * 40 = 5256 square meters

(1) A triangle with a circumference of 12 cm, the circumference of the triangle surrounded by three median lines is——
(2) If the lengths of the three median lines of a triangle are 3cm, 4cm and 5cm respectively, then the area of the triangle is————

A triangle with a circumference of 12 cm and a triangle surrounded by three median lines has a circumference of 6 cm
If the lengths of the three median lines of the triangle are 3cm, 4cm and 5cm respectively,
The original triangle is 6,8,10, which is a right triangle, so the area of this triangle is 24 square centimeters

The square of a ^ 2-1 / 2A + 1 * a ^ - A / A is - 2A + 1-A + 1 / 1, where a = - 2 / 1

=(2a + 1) / (a + 1) (A-1) × (A-1) & # / a (A-1) - 1 / (a + 1) = (2a + 1) / a (a + 1) - 1 / (a + 1) = (2a + 1-A) / a (a + 1) = 1 / a when a = - 1 / 2, the original formula is 1 / (- 1 / 2) = - 2. Your writing of numerator denominator is contrary to the conventional writing. Please understand my writing of numerator / denominator. This is the standard writing

The riddle is "Yue Jun",

Dizzy
Confused → Yue Jun
(dizziness = day)

Primary school science experiment teaching plan

Content: measure the number of breathing and heartbeat in one minute
Lesson 3, unit 4, grade 4, Volume 1, science and Education Press
Teacher: Lei Yiwu teaching time: April 17, 2011
Setting: Sichuan Kaijiang Changling central school
Topic: how will it beat
The purpose of the experiment is to realize that exercise can affect our breath and heartbeat, which are related to exercise
Key points of the experiment: know that exercise can make people's breathing and heartbeat speed up quickly, and breathing and heartbeat will slowly return to normal state after rest
Difficulty: learn to measure your breathing and heart rate correctly
Experimental equipment: self created multi-channel demonstration stethoscope with stopwatch, self created breathing counter
Experiment type: demonstration experiment, student operation
Experimental steps and operation points
Measure the breath and heartbeat in a quiet state for 1 minute  1. The teacher demonstrates the multi-channel demonstration stethoscope with a stopwatch, measures the heartbeat, and focuses on demonstrating that it is very important to determine the position of the heart (the heart is located on the left side of the human chest)
2. Guide the correct use of stopwatch. Timing should be accurate
3. The students are divided into groups, and the heart rate of one minute is measured by the multi-channel demonstration stethoscope with stopwatch under the quiet state. It is better for the students to measure each other. Three or five students can listen at the same time at a time
4. Remind the attention points of measuring the number of breaths: take a breath, take a breath is a breath. When people breathe, the nasal cavity, chest, abdominal cavity and other organs participate in activities, and the physical changes are obvious, and students can also feel them. Use the self-made breathing counter to perform the measurement of the number of breaths. (don't be nervous, keep breathing evenly and smoothly, and don't deliberately take a deep breath, etc.)
5. The students were divided into groups to measure their breathing for one minute in a quiet state
6. Record data in the record sheet while measuring
Measure the breathing and heart rate in 1 minute after exercise
The heart rate and respiration of 1 minute were measured immediately after 2 minutes exercise
3. Students should measure in groups and record data in the record sheet while measuring
4. Measure the number of heart beats and breaths per minute after a short rest
Summary of the experiment  summary of the experimental data, found that the resting state and the heart rate and breathing after exercise are different. People need to consume a lot more energy than before, so the number of breathing and pulse beats will increase than before. Everyone's breathing and heart rate are different, but the general breathing is about 20 times, and the heart rate is about 80 times
4. Arrange the equipment and materials
Experimental conclusion: under normal circumstances, students breathe about 20 times per minute, and their heart beats about 80 times. Exercise will make their heart beats and breathing speed up quickly. After rest, their breath and heart beats will slowly return to normal state
Reflection after the experiment: before the experiment, the students knew less about their bodies than I expected. When the students were asked to predict the times of their breathing and heartbeat in one minute in the teaching, the difference of the number was unbelievable, It must be based on their own original knowledge and experience. Although the students have started to train the measurement skills from the third grade, for a long time, the study separated from the real life still makes the students feel strange about numbers
"I breathe about 60 times a minute." "my heart beats about a dozen times a minute." "100 times." "30 times!"... " In the face of these figures, I really feel that children's understanding is very different, but also let me realize the importance of quantitative education for students
After the experiment: I underestimated the wisdom of the students again. "The weather is cold, we wear thick clothes, it is difficult to touch the heart measurement, and sometimes we may not feel it. We use the pulse of touching the wrist to measure, as long as we measure the beating times of the pulse, we can know the beating times of the heart. I also found that: not only the number of breathing and heartbeat will increase after exercise; when crying, when angry, When taking exams, I am very nervous, when walking at night, when I am wronged, when I am frightened, when I do something wrong, when I am scared by others, and so on, which can increase the frequency of breathing and heartbeat
Record of respiratory and heart rate in one minute
 calm state  after two minutes of exercise  longer time after exercise
One minute
Number of times
Heart rate per minute
Primary school science experiment report
School, Kaijiang Changling central school, grade 4, class 1, experimenter
Time  2011-4-17  experiment name  measurement of respiration and heartbeat
Experimental equipment: multi way demonstration stethoscope with stopwatch, breathing counter
My guess: exercise will affect our breathing and heartbeat. The greater the amount of exercise, the more oxygen we consume. We need to speed up the breathing of the lungs to absorb more oxygen
This is what I do: 1. Measure the heart rate with a multi-channel demo stethoscope with a stopwatch, and determine the position of the heart (on the left side of the chest) under the guidance of the teacher
2. Learn the correct use of stopwatch, accurate timing
3. Use the multi-channel demonstration consultation stethoscope with stopwatch to measure one minute's heart rate in quiet state. Students measure each other. Three or five students listen at the same time
4. Measure the number of breaths per minute with a breath counter
Observed phenomenon: two minutes after exercise in a calm state, a long time after exercise
Number of breaths per minute 20 32 25
Beats per minute 85 108 90
I think: under normal circumstances, breathing more than 25 times per minute, heart rate at 80 times; exercise will make the heart rate and breathing quickly accelerate. After rest, breathing, heart rate will slowly return to normal state
Question: when climbing a high-rise building, some students will be out of breath, while some students do not breathe much change?
Instructor: Lei Yiwu
Design of the inquiry activity of measuring breath and heartbeat in primary school science
Lesson 3, unit 4, grade 4, Volume 1, science and Education Press
Teacher: Lei Yiwu teaching time: April 17, 2011
Setting: Sichuan Kaijiang Changling central school
The teaching of this course mainly consists of three parts
First, by guiding the students to recall their body changes before and after the exercise, talk about their feelings after the exercise, stimulate the students to pay attention to the impact of exercise on their breathing and heartbeat, and understand the students' original understanding of the impact of exercise on their breathing and heartbeat
Second, organize the students to collect the data of breathing and heartbeat per minute in three states (static, after exercise and after 3 minutes rest). In this process, the guidance before measurement is very important. Do you want the students to guide the play? The accuracy of the data is the most important when measuring the data, Before the measurement, we should organize the students to discuss "how can we measure the number of respiration and heartbeat more accurately?" and discuss the measurement methods and precautions in detail
Third, organize the students to analyze the three groups of data by using statistical chart, and guide them to find the rules of breathing and heartbeat, as well as the influence of exercise on breathing and heartbeat
1、 Teaching objective: scientific concept: scientific concept
1. Know the times of breathing and heartbeat in normal condition and after exercise;
2. Recognize that exercise affects our breathing and heartbeat, which are related to exercise
3. The human body needs oxygen for exercise. The gas exchange function of the lung absorbs oxygen into the blood and discharges carbon dioxide out of the body
4. The greater the amount of exercise, the more oxygen the body consumes
5. Regular exercise, can increase the body's vital capacity, which is conducive to health
2、 Process and method: scientific inquiry:
1. It can accurately measure the times of breathing, heart beat and pulse in one minute when you are calm, after exercise and after 3 minutes rest after exercise;
2. Be able to analyze the collected data by using the learned mathematical methods;
3. Be able to explain the problems to be studied through the analysis of data;
3、 Emotional attitude and values:
1. Willing to communicate with students, and be able to complete experimental activities in cooperation
2. Can patiently and meticulously complete the measurement of heartbeat and respiration
3. Recognize the significance of the accuracy of scientific data collection;
4、 Teaching focus:
Key point: know that exercise can make people's breathing and heartbeat speed up quickly, and breathing and heartbeat will slowly return to normal state after rest
Difficulty: learn to measure your breathing and heart rate correctly
5、 Teaching preparation: self created multi-channel demonstration consultation stethoscope with stopwatch, straw, self created breathing counter
6、 Process design of teaching activities: 1
1、 Import
1. Talk: do you like sports? Talk about what sports you usually do. What changes will our body have after and before sports? When students talk about faster breathing and heartbeat, ask students: do you know why our breathing and heartbeat speed up after sports?
(design intention: by guiding students to recall their body changes after exercise and talk about their feelings after exercise, it leads to the fact that the number of heartbeat and breathing changes before and after exercise, which paves the way for later teaching. At the same time, it also stimulates students' attention to the influence of exercise on respiration and heartbeat, and stimulates students' interest in learning, Prepare for other teaching activities of the unit)
2. It seems that the change of the number of people's breathing and heartbeat before and after exercise is the most obvious. Have you measured the number of people's breathing and heartbeat before and after exercise? Let's share this lesson