The knowledge points of the eighth grade of mathematics are summarized in the second volume.
Formulas and attributes:
(1) Sum of internal angles of triangle: The sum of internal angles of triangle is 180.
(2) the nature of the triangle exterior angle:
Property 1: One outer angle of a triangle is equal to the sum of two inner angles that are not adjacent to it.
Property 2: The outer angle of a triangle is larger than any inner angle that is not adjacent to it.
(3) The formula of the sum of polygon internal angles: Is the sum of polygon internal angles equal to? 180
(4) Sum of polygon external angles: the sum of polygon external angles is 360.
(5) Number of diagonal lines of a polygon: ① Starting from a vertex of a polygon, a diagonal line can be drawn to divide the polygon into triangles. ② The polygon * * * has a diagonal line.
Position and coordinates
1, determine the location
In a plane, two data are usually needed to determine the position of an object.
2. Plane rectangular coordinate system
Meaning: In a plane, two mutually perpendicular axes with a common origin form a plane rectangular coordinate system.
(2) Usually, the two number axes are placed in horizontal and vertical positions respectively, and the right and upward directions are the positive directions of the two number axes respectively. The horizontal axis is called X axis or horizontal axis, and the vertical axis is called Y axis and vertical axis, both of which are collectively called coordinate axes, and their common origin O is called the origin of rectangular coordinate system.
③ Establish a plane rectangular coordinate system, and the points on the plane can be represented by a set of ordered real number pairs.
(4) In the plane rectangular coordinate system, two coordinate axes divide the coordinate plane into four parts, the upper right part is called the first quadrant, and the other three parts are called the second quadrant, the third quadrant and the fourth quadrant counterclockwise, and the points on the coordinate axes are not in any quadrant.
⑤ In the rectangular coordinate system, for any point on the plane, there is an ordered real number pair (that is, the coordinates of the point) corresponding to it; On the contrary, for any ordered real number pair, there is a point on the plane corresponding to it.
Eighth grade mathematics knowledge points Shanghai campus edition
Addition and subtraction of fractions
1. Although general fractions and reduction are aimed at fractions, they are two opposite variants. Reduction is for one score, while general scores are for multiple scores. The approximate fraction is a simplified fraction, and the general fraction is a simplified fraction, thus unifying the denominator of the fraction.
2. Both general score and approximate score are deformed according to the basic properties of the score, and their similarity is to keep the value of the score unchanged.
3. The general denominator is written in the form of unexpanded continuous product, and the numerator multiplication is written in polynomial to prepare for further operation.
4. Total score basis: the basic nature of the score.
5. The key to general division is to determine the common denominator of several fractions.
Usually, the product of the powers of all factors of each denominator is taken as the common denominator, which is called the simplest common denominator.
6. By analogy, get the total score of this score:
Changing several fractions with different denominators into fractions with the same mother equal to the original fraction is called the general fraction of fractions.
7. The rules for adding and subtracting fractions with the same denominator are: adding and subtracting fractions with the same denominator and adding and subtracting numerators with the same denominator.
Addition and subtraction of fractions with the same denominator, denominator unchanged, addition and subtraction of molecules, that is, the operation of fractions is transformed into the operation of algebraic expressions.
8. Fraction addition and subtraction law of different denominators: Fractions of different denominators are added and subtracted, first divided by fractions of the same denominator, and then added and subtracted.
9. Fractions with the same denominator are added and subtracted, and the denominator remains the same. Add and subtract molecules, but pay attention to each molecule as a whole, and put parentheses in due course.
10. For the addition and subtraction between the algebraic expression and the fraction, the algebraic expression is regarded as a whole, that is, it is regarded as a fraction with the denominator of 1, so as to divide.
1 1. For addition and subtraction of fractions with different denominators, first observe whether each formula is the simplest fraction. If the fraction can be simplified, it can be simplified first and then divided, which will simplify the operation.
12. As the final result, if it is a score, it should be the simplest score.
Summary of mathematical knowledge points in the second volume of the second day of junior high school Beijing Normal University Edition
Chapter 1 One-dimensional linear inequalities and one-dimensional linear inequalities.
First, the unequal relationship.
1, generally, the formula connected by the symbol ""(or "≥") is called inequality.
2. Distinguish between equality and inequality: equality represents an equal relationship; Inequality represents an unequal relationship.
3. Accurately "translate" inequalities and correctly understand mathematical terms such as "non-negative number" and "not less than".
nonnegative number
Nonpositive number
Second, the basic properties of inequality
1, master the basic properties of inequality and use it flexibly:
Add (or subtract) the same algebraic expression on both sides of inequality (1), and the direction of inequality remains unchanged, that is:
If a>b, then A+C > b+c，a-c & gt； b-c。
(2) Both sides of the inequality are multiplied by (or divided by) the same positive number, and the direction of the inequality remains unchanged, that is,
If a>b and c>0, then ac> BC,
(3) When both sides of the inequality are multiplied by (or divided by) the same negative number, the direction of the inequality changes, namely:
If a>b and c < 0, ac
2. Comparison size: (A and B represent two real numbers or algebraic expressions respectively)
Generally speaking:
If a>b, then a-b is a positive number; On the other hand, if a-b is positive, then a >；; b；
If a=b, then a-b is equal to 0; On the other hand, if a-b is equal to 0, then a = b；;
If a
Namely:
a & gtb & lt= = = & gta-b & gt； 0
a = b & lt= = = & gta-b=0
aa-b & lt； 0
It can be seen that to compare the sizes of two real numbers, just look at their differences.
The eighth grade mathematics second volume knowledge point arranges the related article;
★ The arrangement of mathematics knowledge points in the second volume of the eighth grade
★ Knowledge point induction and mathematics learning methods in the second volume of junior two mathematics.
★ Summarize the mathematics knowledge points in the second volume of the eighth grade.
★ Summarize the mathematics knowledge points in the second volume of the eighth grade.
★ Summary of Mathematical Knowledge Points in the Second Volume of Grade 8
★ Combing the knowledge points of mathematics in the second volume of the eighth grade
★ General review of mathematics knowledge points in the second volume of the eighth grade
★ Summary of Mathematical Knowledge Points in Volume II of Grade 8 of People's Education Edition
★ Summary of Mathematical Knowledge Points in the Second Volume of Grade 8
★ Summary of key knowledge in the second volume of second grade mathematics.