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

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

3. Circumference = pi × diameter =πd= pi × radius× 2 = 2π r.

4. Area of rectangle = length× width S=ab

5. Area of a square = side length × side length S=a?

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

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

Eight, trapezoidal area = (upper bottom+lower bottom) × height ÷2S=(a+b)h÷2.

Nine, diameter = radius ×2d=2r

X. radius = diameter ÷2r=d÷2

XI。 Area of circle = π× radius× radius

12. Area of triangle = base × height ÷2S=a×h÷2.

Thirteen, square area = side length x side length s = a x a

14. area of rectangle = length× width S=a×b

15. area of parallelogram = base× height s = a× h.

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

Sum of internal angles: sum of internal angles of triangle = 180 degrees.

Eighteen, cuboid volume = length x width x height V=abc.

Nineteen. Volume of cuboid (or cube) = bottom area × height V=Sh

Twenty, the volume of the cube = side length x side length x side length V=aaa.