Basic knowledge points of mathematics in the first volume of the fourth grade
1, line
(1) straight line
A straight line has no end; Infinitely long; You can draw countless lines after one o'clock, and only one straight line after two o'clock.
(2) Ray
Ray has only one endpoint; Infinitely long.
⑶ line segment
A line segment has two endpoints, which are part of a straight line; Limited length; In the connection between two points, the segment is the shortest.
The length of the line segment between two points is the distance between two points.
Connection of straight ray line segments: all are straight lines, and both rays and line segments are part of a straight line.
(4) The positional relationship between two straight lines in the same plane is parallel and intersecting.
5] parallel lines
Two straight lines defined on the same plane and not intersecting are called parallel lines. The straight line A is parallel to B, and the straight line B is also parallel to A. ..
At a point outside the straight line, you can only draw a straight line parallel to the known straight line.
There are countless vertical segments between two parallel lines, all of which are equal in length. The vertical segments between parallel lines are equal everywhere.
The painting method is one in two, three moves and four paintings.
[6] vertical line
When two straight lines intersect at right angles, they are said to be perpendicular to each other, one of them is said to be perpendicular to the other, and the intersection point is called vertical foot.
nature
After a point (on or off the line), you can only draw a straight line perpendicular to the known straight line.
The vertical line segment drawn from a point outside the straight line is the shortest, and its length is called the distance from that point to the straight line.
The painting method is one in two, three in three and four in four.
2. Angle
The definition of (1) angle leads to two rays from a point, and the graph is called an angle. This point is called the vertex of the angle, and these two rays are called the edges of the angle.
(2) Angle measurement Angle measurement unit is "degree", with the symbol "". Divide the semicircle into 180 equal parts, and the angle of each part is 1 degree. Write "1".
(3) Comparison of the size of the angle The size of the angle has nothing to do with the length drawn on both sides of the angle. The size of the angle depends on the size of both sides. The bigger the fork, the bigger the angle.
(4) The drawing method of angle is to draw a line, measure the angle, connect three lines and mark four. The angle a pair of triangles can draw is a multiple of 15.
(5) Classification of angles
① Acute angle: An angle less than 90 is called an acute angle.
② Right angle: An angle equal to 90 is called a right angle.
(3) Oblique angle: An angle greater than 90 and less than180 is called obtuse angle.
4 flat angle: the two sides of the angle form a straight line, and the angle formed is called flat angle. Boxer 180.
⑤ Fillet: One side of the corner rotates once and coincides with the other side. Fillet 360.
Mathematics knowledge point grade four
Algorithms and simple operations
First, the law of addition:
1, additive commutative law: Two numbers are added, the addend positions are exchanged, and the sum is unchanged. a+b=b+a
2, the law of addition and association: three numbers are added, you can add the first two numbers first, and then add the third number; Or add the last two numbers first, and then add the first number, and the sum remains the same. (a+b)+c=a+(b+c)
These two laws of addition are often used together.
For example:165+93+35 = 93+(165+35) What is the basis?
3. The essence of continuous subtraction: one number subtracts two numbers continuously, which is equal to the sum of this number MINUS those two numbers. a-b-c=a-(b+c)
Second, the law of multiplication:
1, multiplication method of substitution: When two numbers are multiplied, the exchange factor position remains unchanged. a×b=b×a
2. Multiplication and association law: When three numbers are multiplied, you can multiply the first two numbers and then the third number, or you can multiply the last two numbers and then the first number, and the product remains unchanged. (a×b)×c=a×(b×c)
These two multiplication laws are often used in combination. Such as: 125×78×8.
3. Multiplication and distribution law: the sum of two numbers is multiplied by one number. You can multiply these two numbers by this number first, and then add up the products.
(a+b)×c=a×c+b×c (a-b)×c=a×c-b×c
Mathematics learning methods and skills
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.
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