1, the perimeter of the rectangle = (length+width) ×2 C=(a+b)×2.
2. The circumference of a square = side length ×4 C=4a.
3. Area of rectangle = length× width S=ab
4. Area of a square = side length × side length S = a× a.
5. Area of triangle = base × height ÷2 S=ah÷2.
6. parallelogram area = bottom x height S=ah
7. trapezoidal area = (upper bottom+lower bottom) × height ÷ 2s = (a+b) h ÷ 2.
8. Diameter = Radius× 2D = 2r Radius = Diameter ÷2 r= d÷2
9. The circumference of a circle = π× diameter = π× radius× 2c = π d = 2π r.
10, area of circle = π× radius× radius.
1 1, triangle area = base × height ÷2. The formula S= a×h÷2.
12, square area = side length × side length formula s = a× a.
13, area of rectangle = length× width formula s = a× b.
14, area of parallelogram = base× height formula s = a× h.
15, trapezoidal area = (upper bottom+lower bottom) × height ÷2 formula S=(a+b)h÷2.
16, sum of internal angles: sum of internal angles of triangle = 180 degrees.
17, cuboid volume = length× width× height formula: V=abh.
18, cuboid (or cube) volume = bottom area × height formula: V=abh.
19, volume of cube = side length × side length × side length formula: V=aaa.
20. circumference = diameter × π formula: L = π d = 2π.