1, triangle perimeter formula: perimeter = sum of side lengths.
2. Triangle area formula: area = bottom × height ÷2.
3. Rectangular area formula: area = length × width.
4. parallelogram area formula: area = bottom × height.
5. The circumference formula of a circle: circumference =2×π× radius.
6. Area formula of circle: area = π× radius? .
7. The square of the sum of two numbers: (a+b)? =a？ +2ab+b？ .
8. The square of the difference between two numbers: (a-b)? =a？ -2ab+b？ .
9. Formula for finding the root of quadratic equation: x = [-b √ (b? -4ac)]2a .
10, average formula: average = sum of all data ÷ number of data.
Junior high school mathematics learning skills
1, master the basic knowledge: junior high school mathematics is the basic stage of mathematics. To learn mathematics well, we must master basic concepts and skills.
2. Understanding concepts: Mathematics is a conceptual subject, and it is necessary to understand the essence and meaning of each concept, rather than just memorizing the definition.
3, a lot of practice: math learning needs a lot of practice. By doing problems, you can deeply understand concepts and skills, and at the same time improve your problem-solving ability.
4. Independent thinking: Mathematics learning needs independent thinking, not only relying on teachers or classmates' explanations, but thinking, analyzing and solving problems by yourself.
5. Be good at summarizing: Mathematics learning needs to be good at summarizing, summarizing knowledge points and problem-solving methods in time, which can deepen understanding and prepare for the senior high school entrance examination.