A perimeter is the sum of the sides of a polygon.
A circumference is the distance around the circle.
Perimeter of a Triangle
a. Any Triangle
Let a, b and c are the sides of the triangle
P = a + b + c
b. For Isosceles Triangle
Let a = length of congruent sides
b = base of the third side
P = 2a + b
c. For Equilateral Triangle
Let s = side
P = 3s and s = P ÷ 3
Perimeter of a Quadrilateral
a. Any Quadrilateral
Let a, b, c, and d be the sides
P = a + b + c + d
b. Square
Let s = side
P = 4s and s = P/4
c. Rectangle
Let l = length
w = width
P = 2l + 2w or P = 2 ( l + w )
l = P ÷ 2 - w
w = P ÷ 2 - l
Perimeter of Any Regular Polygon
To find the perimeter of a regular polygon, multiply the number of sides by the length of a side.
Let s = side
P = ns
Pentagon P = 5s
Hexagon P = 6s
Heptagon P = 7s
Octagon P = 8s
Circumference of a circle
Let D = diameter
C = circle
r = radius
C = πD or C = 2πr
D = 2π or D = C ÷ π
Where π = 3.1416
r = D ÷ 2 or r = C ÷ 2π
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