Knowledge points of mathematics "angle measurement" in the first volume of the fourth grade of People's Education Press
1. Line, light, angle
Straight line: a line that extends infinitely to both ends and has no end.
Ray: it can be like a line extending in one direction, and the ray has an endpoint.
Line segment: a line that cannot be extended. A line segment has two endpoints.
Angle:
A figure composed of two rays with a common endpoint is called an angle.
This common endpoint is called the vertex of the angle, and these two rays are called the two sides of the angle.
2. The connection and difference between straight lines, rays and line segments.
1) Both lines and rays can extend indefinitely, so the length cannot be measured.
2) The length of the line segment can be measured.
3) A line segment has two endpoints, a straight line has no endpoint, and a ray has only one endpoint.
3. The characteristics of angle
A corner has a vertex and two sides.
The angle is usually represented by the symbol "∞"
4. Angle size comparison:
The unit of measurement of angle is "degree", and the symbol is "degree". The semicircle is divided into 180 equal parts, and the angle of each equal part is l degrees. Record it as 1, and measure the angle with a protractor.
Knowledge points of mathematics "hectares and square kilometers" in the first volume of the fourth grade of People's Education Edition
1. The area units that have been learned are square centimeter (cm2), square decimeter (dm2), square meter (m2), hectare and square kilometer (km2).
2.( 1) A square with a side length of 1cm and an area of 1cm.
(2) A square with a side length of 1 decimeter and an area of 1 square decimeter.
(3) A square with a side length of 1m and an area of 1m2.
(4) Square with side length 100 m and area 1 hectare. 1 ha = 1 10,000 m2
The area of land can be measured in hectares.
For example, the Bird's Nest covers an area of about 1 hectare. The area surrounded by the runway 400 is about 1 hectare.
(5) A square with a side length of 1000m and an area of 1 km2.
1 km2 = 100 hectares =1100 million m2.
China has a land area of about 9.6 million square kilometers.
3. Conversion between area units:
(1) First, remember the progress between them:
1 km2 = 100 hectares =1100 million m2.
1 ha = 1 10,000 m2
1 m2 = 100 square decimeter
1 square decimeter = 100 square centimeter
1 m2 = 10000 cm2
(2) conversion method:
○ 1 To convert a high-level unit into a low-level unit, it is necessary to use multiplication to calculate, just multiply the number in front of the high-level unit by the ratio between the two units. (that is, the height, the rate of progress, the decimal point moves to the right, and you can see the rate of progress by moving a few places. )
2 To aggregate low-level units into high-level units, it is necessary to calculate by division, as long as the number in front of the low-level unit is divided by the ratio between two units. (that is, reduce the level, divide by the forward speed, move the decimal point to the left, move a few positions, and see the forward speed. )
A. To convert hectares into square meters, just write four zeros directly after the data in front of hectares.
B, to convert square meters into hectares, just remove four zeros from the data in front of the square meters.
C. To convert a square kilometer into a hectare, just write two zeros directly after the data in front of the square kilometer.
D, convert a square kilometer into a square meter, just add six zeros directly after the data in front of the square kilometer.
E, to convert a square meter into a square kilometer, just remove six zeros from the data in front of the square meter.
4, fill in the legal provisions of the area unit:
(1) Land area, province (including municipality directly under the central government) area, provincial capital city area, state (city) area, county, township area, village committee and village area, generally taking "square kilometers" as the unit.
(2) Parks, colleges (schools), stadiums (gymnasiums), etc. , generally in "hectares" as the unit.
(3) Housing (building) area, classroom area, campus greening area, etc. , are generally measured in square meters.
Learning methods and skills of fourth grade mathematics
0 1, strengthen integer and decimal calculation practice.
The computing power is still too good. The fourth grade must be very skilled in integer calculation and decimal calculation to ensure accuracy and speed, otherwise the fifth grade will focus on learning fractions, and the pressure will be even greater if the integer is not skilled enough. It is suggested to do five calculation problems every day to improve the speed and accuracy of doing them.
02. Cultivate children's good study habits.
The fourth grade is a good time to form study habits, and forming good habits in time is more conducive to future study.
Specifically including:
1. Prepare well before class and review in time after class. Preview before class, understand the knowledge points to be talked about, and it will be better to come to class with questions. It is impossible to master all the knowledge points completely in the limited classroom time. Parents should urge their children to review after class and consolidate the knowledge they have learned in time.
2. Standardize children's writing. With the increase of application problems, children's writing must be standardized, steps and processes should be in place, and the habit of drawing pictures should be formed for the trip. Number theory should be rigorous and standardized.
3. Develop the habit of thinking independently and bravely. What children nowadays lack most is independent thinking, strong dependence, heavy embarrassment and flinching when encountering problems. At this time, children should be encouraged to think independently and develop the habit of loving thinking.
03, at the beginning of winter vacation, do some cup test questions over the years.
Winter vacation began to arrange time to do some real questions over the years, strengthen comprehensive training, and prepare for the spring sprint of various cups.
04. Learning requires perseverance.
For new knowledge, if you want to draw inferences while mastering basic concepts and ideas, you can't do it without practice. Only with proper practice can we consolidate the knowledge points. You often tell your parents that you must keep studying and practice once or twice a day according to a reasonable schedule to ensure uninterrupted practice.
Summarize the knowledge points of fourth grade mathematics;
★ Summarize the knowledge points of the first volume of mathematics in the fourth grade of primary school.
★ Summarize and sort out the knowledge points of fourth grade mathematics.
★ Summarize the knowledge points of fourth grade mathematics.
★ Summary of knowledge points in the fourth grade of the first volume of mathematics
★ Summarize the knowledge points of fourth grade mathematics.
★ Organize the knowledge points of fourth grade mathematics.
★ Summary of Mathematics Knowledge Points in Grade Four
★ Summary of Mathematics Knowledge Points in Grade Four
★ Summary of Mathematics Knowledge Points in Grade Four
★ Summarize the knowledge points of the fourth grade mathematical triangle.