Knowledge points of mathematical rational numbers
1. Classification of rational numbers: rational numbers include integers and fractions, integers include positive integers, 0 and negative integers, and fractions include positive and negative fractions. "Classification" principle: (1) proportionality (no weight, no leakage); (2) There are standards.
2. Non-negative number: the collective name of positive number and zero.
3, the opposite number:
(1) Definition: If the sum of two numbers is 0, the two numbers are opposite.
(2) Formula for finding the inverse number: the inverse number of A is-A. ..
(3) Properties: ① When a ≠ 0, A ≠-A;
② The positions of A and -a on the number axis are symmetrical about the origin;
③ The sum of two opposites is 0 and the quotient is-1.
Junior high school similar triangles kaodian
Test center: similar triangles's concept, the meaning of similarity ratio, and the enlargement and reduction of drawing graphics.
Assessment requirements: (1) Understand the concept of similarity; (2) Grasping the characteristics of similar figures and the significance of similarity ratio, we can enlarge and reduce the known figures as needed.
Test sites: the proportion theorem of parallel lines and the related theorem of parallel lines on one side of a triangle.
Examination requirements: Use the proportional theorem of parallel lines to understand and solve some geometric proofs and geometric calculations.
Note: An edge judged to be parallel cannot be used as the corresponding line segment in the condition in proportion.
Test site: similar triangles's concept
Evaluation requirements: Based on the concept of similar triangles, master the characteristics of similar triangles and understand the definition of similar triangles.
Knowledge points of mathematical symmetric graphics
Axisymmetric graphics: line segment, angle, isosceles triangle, equilateral triangle, diamond, rectangle, square, isosceles trapezoid and circle.
Number of symmetry axes: an angle has a symmetry axis, that is, the angle bisector of the angle; The isosceles triangle has an axis of symmetry, which is the median vertical line of the base; An equilateral triangle has three axes of symmetry, that is, the median vertical lines on three sides; A diamond has two symmetry axes, which are straight lines where two diagonals are located, and a rectangle has two symmetry axes, which are straight lines between two groups of opposite sides.
Centrally symmetric figures: line segments, parallelograms, diamonds, rectangles, squares and circles.
Symmetry center: the symmetry center of the line segment is the midpoint of the line segment; The symmetrical center of parallelogram, rhombus, rectangle and square is the intersection of diagonal lines, and the symmetrical center of circle is the center of circle.
Description: Line segments, diamonds, rectangles, squares and circles are all symmetrical figures.
The above is my summary of junior high school mathematics knowledge points for your reference only, and I hope it will help you.