Additive commutative law: A+B = B+A.

Additive associative law: (a+b)+c=a+(b+c)

Multiplicative commutative law: ab=ba

Law of multiplicative association: (ab)c=a(bc)

Multiplication and distribution law: a(b+c)=ab+ac.

Second, the geometric figure calculation formula

(1) circumference: the length of a circle around an object.

① Rectangular perimeter = (length+width) ×2 C=(a+b)×2

② Square perimeter = side length ×4 C=4a

③ Circumference = pi× diameter = pi× radius× 2c = π dc = 2π r.

(2) area: that is, the size of the surface or closed figure of an object.

① area of rectangle = length× width S=ab

② Area of a square = side length × side length S=a? a=a2

③ area of parallelogram = base × height S=ah

④ Area of triangle = base × height ÷2 S=ah÷2.

⑤ Trapezoidal area = (upper bottom+lower bottom) × height ÷2 S=(a+b)h÷2.

⑥ area of circle = pi× radius S=πr2.

⑦ diameter d=2r radius = diameter ÷2 r= d÷2.

⑧ Annular area = outer circle area-inner circle area S ring = outer circle-The area formula of interconnected plane figures in S is based on the rectangular area calculation formula. For example, two identical triangles and trapezoids can be combined into a parallelogram. The length of a circle is 1/2C and the width is r 。

(3) Surface area: The sum of the areas of all faces of a solid figure is called its surface area.

① The surface area of a cuboid = (length× width+length× height+width× height )× 2s = 2 (AB+AH+BH).

② Surface area of cube = side length× side length× 6s = a× a× 6 = 6a2.

③ lateral area of cylinder = bottom circumference x height S=Ch =2πrh.

④ Surface area of cylinder = lateral area+bottom area ×2 S= Ch+2πr2 = 2πrh+2πr2 Note: When the circumference of cylinder bottom is equal to height, the lateral expansion is square, and c = H2 π r = H.

(4) Volume: The size of the space occupied by an object is called volume.

① cuboid volume = length× width× height V=abh

② The volume of the cube = side length × side length× side length V=a×a×a=a3.

③ Cylinder volume = bottom area × height V=sh=πr2h

④ Volume of cone = bottom area × height ÷ 3 v =1/3sh =1/3π r2h The volume formula of cuboid, cube and cylinder can be unified as: V=sh, that is, bottom area × height. Long, positive, equal volume and equal bottom cylinders and cones, the height of which is three times that of cuboids, cubes and cylinders.