Formula for Calculating the perimeter and area of a triangle, rectangle, square, trapezoid, or circle

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What is the formula for calculating the perimeter and area of a triangle, rectangle, square, trapezoid, or circle?

Perimeter: girth area: Area

1. Triangle (General triangle, Helen formula)

Triangle

Perimeter L = A + B + C (a, B, c is the length of the three sides of the triangle, the same below)
Area S = √ [P (P-A) (p-B) (p-C)], P = (1/2) (A + B + C)

2. rectangle

Rectangle

Perimeter L = 2 (a + B) (a, B is the length of the adjacent side of the rectangle, the same below)
Area S = AB

3. Square

Square

Perimeter L = 4A
Area S = a ^ 2

4. Trapezoid

Trapezoid

Perimeter L = A + B + C + D (A: Upper bottom, B: lower bottom, c, d Two waist lengths, the same below)
Area S = (1/2) (a + B) H (H: trapezoid height)

5. Circle

Circle

Perimeter L = 2 π R (π: circumference rate, R: circle radius, the same below)
Area S = π R ^ 2