What are the mathematical formulas in the second volume of the seventh grade?

The mathematical formula of the second volume of grade seven is as follows:

1. The circumference of the rectangle = (length+width) ×2, and C=(a+b)×2.

Second, the perimeter of the square = side length ×4, C=4a.

Third, the area of a rectangle = length × width, and S=ab.

4. Square area = side length × side length, S = a.a = a 2.

V area of triangle = base × height ÷2, S=ah÷2.

Six, parallelogram area = bottom x height, S=ah.

Seven, trapezoidal area = (upper bottom+lower bottom) × height ÷2, s = (a+b) H ÷ 2.

Eight, circumference = pi× diameter = pi× radius× 2, c=πd=2π.