Learning knowledge should be good at thinking, thinking and thinking again. Every subject has its own learning method, but it is always inseparable from it. Mathematics, as one of the most brain-burning subjects, also needs to be memorized, memorized and practiced. The following are some eighth-grade math knowledge points I have compiled for you, hoping to help you.

Eight-grade mathematics knowledge points

A preliminary understanding of statistics

1, broken-line statistical chart: you can get the information of data changes and make simple predictions.

2. The method of broken-line statistical chart: on the grid paper, mark the points according to the given data, and then connect the points with lines in order.

3. Be able to see the information provided by the dotted statistical chart and answer related questions.

Supplementary content:

1. The difference between a bar chart and a line chart: a bar chart indicates the quantity with a straight line, and a line chart indicates the change of quantity with a broken line.

2. Have a preliminary understanding of the statistical chart of compound broken lines, from which we can get the corresponding information and answer the questions raised.

homework

1. The basic meaning of statistics is (d).

A. Statistical information

B. Statistics

C. Statistical activities

D is the science of data processing methods and techniques, or statistics is the science of studying "data". The task is how to effectively collect, sort out and analyze these data, explore the inherent quantitative regularity of the data, and make inferences or predictions about the observed phenomena until it provides a basis for decision-making.

2. Understand the production and operation of state-owned industrial enterprises in a certain area, and the overall statistics are (b).

A. Every state-owned industrial enterprise

B. All state-owned industrial enterprises in the region

C. Production and operation of all state-owned industrial enterprises in this region

D. Every enterprise

3. To understand the learning situation of 20 students, the overall unit is (C).

A.20 students

B. Learning situation of 20 students

C. Every student

D. Learning situation of each student

4. Among the following items, (b) is a quantitative symbol.

A. Gender

B. Age

C. Professional title

D. Health status

The second volume of the second day of junior high school summarizes the knowledge points of mathematics.

Random surprise inspection

(1) The survey sample is randomly selected, and the probability of each unit being selected in the population is equal. Therefore, it can ensure the uniform distribution of the selected units in the whole population, and there will be no bias error, which is very representative.

(2) Take all sample units as a "delegation" and use the whole "delegation" to represent the whole. Instead of using randomly selected individual units to represent the whole.

(3) The number of selected survey samples is determined by scientific calculation according to the requirements of survey error, and there is a reliable guarantee on the number of survey samples.

(4) The error of sampling survey can be calculated according to the overall difference between the number of samples and the units before the survey, and controlled within the allowable range, so the accuracy of the survey results is high.

homework

1. the sampling score is a (a)

A. structural relative number B. proportional relative number C. comparative relative number D. intensity relative number

2. The relationship between percentage and variance of percentage is (c)

A. The closer the score is to 0, the greater the variance of the score. B. The closer the score is to 1, the greater the variance of the score.

C. The closer the score is to 0.5, the greater the variance of the score. D. The closer the score is to 0.25, the greater the variance of the score.

3. Cluster sampling is a comprehensive survey of the sampled group, so cluster sampling is (b)

A. Comprehensive investigation B. Incomplete investigation C. One-time investigation D. Recurrent investigation

4. Select 19% of 400 college students for non-repeated sampling survey, in which the proportion of top students is 20% and the probability guarantee degree is 95.45%, then the limit sampling error of the proportion of top students is (a).

4. 13% c 9. 18% d 8.26%

5. According to the sampling data of 5%, the qualified rate of product A is 60%, and that of product B is 80%. When the number of sampled products is equal, the sampling error of qualified rate is (b).

A.a product is big, B. B product is big, C. equals D. It is impossible to judge.

Eight-grade mathematics knowledge points

Diamond decision theorem

1. A set of parallelograms with equal adjacent sides is a diamond.

2. Parallelograms with diagonal lines perpendicular to each other are diamonds.

A quadrilateral with four equilateral sides is a diamond. S diamond = 1/2×ab(a and B are two diagonal lines).

Definition of a square: a diamond with right angles or a rectangle with equal adjacent sides.

The essence of a square: all four sides are equal and all four corners are right angles. A square is both a rectangle and a diamond.

Square judgment theorem;

1. A rectangle with equal adjacent sides is a square.

Diamonds with right angles are squares.

Definition of trapezoid: A set of quadrangles with parallel opposite sides and another set of quadrangles with non-parallel opposite sides are called trapezoid.

Definition of right-angled trapezoid: a trapezoid with a right angle.

Definition of isosceles trapezoid: isosceles trapezoid.

The nature of isosceles trapezoid: the two angles on the same base of isosceles trapezoid are equal; The two diagonals of an isosceles trapezoid are equal.

Judgment theorem of isosceles trapezoid: two trapezoid with equal angles on the same base are isosceles trapezoid.

Auxiliary lines commonly used to solve trapezoidal problems are shown in the figure.

The center of gravity of the line segment is the midpoint of the line segment. The center of gravity of a parallelogram is the intersection of its two diagonals. The point of doubt when three center lines of a triangle meet is the center of gravity of the triangle. A rectangle with an aspect ratio of-1 (about 0.6 18) is called a golden rectangle.

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