1, multiplication formula table: the product of each row and column is a number, such as "11, 21, 42, 31" and so on.

2. additive commutative law and the law of association: exchange the positions of two addends, and the sum is unchanged; Combine the addition of three or more numbers, first add the first two numbers, then add the third number in turn, and the sum is unchanged.

3. The essence of subtraction: subtracting several numbers in a row from a number is equivalent to subtracting the sum of these numbers from this number.

4. Commutative law and associative law of multiplication: exchange the positions of two factors, and the product remains unchanged; When three or more numbers are multiplied, the first two numbers are multiplied first, and then the third number is multiplied in turn, and the product is unchanged.

5. The essence of division: a number divided by several numbers is equal to the product of this number divided by these numbers.

6. Axisymmetric property: a graph is folded in half along a straight line, and the graphs on both sides can completely overlap, which is an axisymmetric graph.

7. Theorem of the sum of triangle internal angles: the sum of triangle internal angles is equal to 180 degrees.

8. Triangle area formula: area = bottom × height ÷2.

9. trapezoidal area formula: area = (upper bottom+lower bottom) × height ÷2.

10, the circumference formula of a circle: circumference = diameter × π (π takes 3. 14).

1 1, area formula of circle: area = radius? ×π (π takes 3. 14).