1, rectangle

Circumference = (length+width) ×2 C=(a+b)×2

Area = length × width S=ab

2. Square

Perimeter = side length ×4 C=4a

Area = side length x side length S=a.a= a2

Step 3: Triangle

Perimeter = sum of three sides C=a+b+d area = bottom × height ÷2 S=ah÷2 4. The perimeter of parallelogram = twice the sum of two adjacent sides C = (a+b) × 2;

Area = one side × height of this side S=ah

5, trapezoidal

Perimeter = the sum of the lengths of four sides C = A+B+D+E.

Area = (upper bottom+lower bottom) × height ÷ 2s = (a+b) h ÷ 2.

6.diamond shape

Perimeter = side length ×4 C=4a

Area = half of diagonal product s=ab÷2

7.circle

Circumference = pi× diameter = pi× radius× 2c = π d = 2π r;

Area = π× square of radius S=π r2

Ringed

Area = π× (square of long radius-square of short radius)

The circumference of a semicircle = 2πr/2+ diameter = πr+2r.

8. Fan-shaped

Circumference = radius ×2+ arc length c = 2r+(n÷ 360) π r = 2r+(n÷180) π r.

Area s = π R2

N÷360=I/2lR (where L is arc length)

Second, solid geometry:

1, cuboid

Surface area = (length× width+length× height+width× height) ×2

Volume = length× width× height V =abh

2. Cubic

Surface area = side length × side length× ×6 S =6a

Volume = side length x side length x side length v = a.a. a=a 3

Step 3: Cylinder

Transverse area = perimeter of bottom circle x height S=ch.

Volume = bottom area × height v = shv = π rh = π (d ÷ 2) h = π (c ÷ 2 ÷ π) h h.

Surface area = upper and lower bottom area+side area S = 2π r+2π rh = 2π (D÷2)+2π (D÷2) h = 2π (C2÷2÷π)+ch.

4. Cone

Surface area =S side +S bottom = π rl+π r 2, where S side = 1/2α l 2 = π rl.

Volume product = bottom area × height ÷ 3v = sh ÷ 3 = π r h ÷ 3 = π (d ÷ 2) h ÷ 3 = π (c ÷ 2 ÷ π) h ÷ 3.

Third, other irregular geometric figures can be calculated by methods such as segmentation.

Extended data:

Solid geometry can be divided into the following categories:

(1) cylinder: including cylinder and prism. Prisms can be divided into straight prisms and oblique prisms, and can be divided into triangular prisms, quadrangular prisms and n prisms according to the number of sides of the bottom; The volume of the prism is equal to the area of the bottom multiplied by the height, that is, V = SH.

(2) Cone: including cone and pyramid, divided into triangular pyramid, quadrangular pyramid and N pyramid; The volume of the pyramid is

(3) Rotating body: including cylinder, frustum, cone, sphere, spherical crown, bow ring, circular ring, dike ring, fan ring, jujube pit, etc.

(4) Section: including frustum, frustum, truncated cylinder, truncated prism, truncated cone, spherical crown, spherical notch, etc. Its surface area and volume are generally solved by digital addition and subtraction.

Plane geometry can be divided into the following categories:

(1) circle: including perfect circle, ellipse and multifocal circle-ellipse.

(2) Polygons: triangles, quadrangles, pentagons, etc.

(3) Bows: excellent bows, poor bows, parabolic bows, etc.

(4) Multi-arcs: crescent moon, pattern, Tai Chi, gourd, etc.

Baidu encyclopedia-geometry