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

2. Area of rectangle = length× width S=a×b

3. The circumference of a square = side length ×4 C=a×4.

4. Area of a square = side length × side length S = a× a.

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

6. parallelogram area = bottom x height s = a x h.

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

8. Circumference = π× diameter C=π×d

9. Area of circle = π× radius× radius S=πrr

10, the surface area of a cuboid = (length× width+length× height+height× width) ×2.

1 1, the surface area of the cube = side length× side length× ×6 S table =a×a×6.

12, lateral area of cylinder = perimeter of bottom× height of S side = bottom of C side× h.

13, cylinder surface area =Side surface area +2 bottom surface areas s table = s side +2 S bottom.

14. Surface area of cone = lateral area of cone+area of bottom circle s table =S side +S bottom.

15, the area of the ring = the area of the outer circle-the area of the inner circle s = the outer circle-the inner circle.

16, the perimeter of parallelogram = (long side+short side) ×2 S=(a+b)×2.

Extended data:

Plane figure classification

First of all, according to the angle

Acute triangle, obtuse triangle, right triangle, right trapezoid

Second, divide by edge.

Isosceles triangle, equilateral triangle, equilateral triangle, quadrilateral, pentagon

Third, according to the symmetry axis

1, regular triangle, square, regular pentagon, regular polygon

2. Rectangle: Two groups of opposite sides are equal in length, parallel to each other and unstable. It is a special parallelogram with two symmetrical axes.

3. Square: an unstable and special rectangle with completely equal sides.

4, parallelogram, unstable, no symmetry axis.