For example, a pentagon has five sides, and you need to know the length of each one to determine perimeter. Even with an irregular polygon that has 20 sides, you can still find the perimeter as long as you know the length of each side.
Say the irregular pentagon has the following lengths: A = 4, B =2, C = 3, D = 3, and E = 2 Add 4 + 2 + 3 + 3 + 2 = 14, where P (perimeter) = 14
Find the sum of all the sides: P = 14a + 11b + 7a Combine the like terms: P = (14a + 7a) + 11b P = 21a + 11b
To start, find the radius of the circle, which is the length of a line segment running from the center of the circle to the perimeter. For simpler equations, use the truncated version π = 3. 14 For a circle with a radius of 4cm: C = 2 x 3. 14 x 4 = 25. 12cm
On a square where x = 3cm, then P = 4 x 3 = 12cm
P = (2 x 8) + (2 x 5) P = 16 + 10 P = 26cm The equation P = 2(l + h) will also give you the same result: 2(8 + 5) = 2(13) = 26cm[5] X Research source
For a quadrilateral with no equal sides, like an irregular trapezoid, use the equation P = a + b + c + d For a quadrilateral with four equal sides, use the same equation as a square: P = 4x. For quadrilaterals where the lengthwise sides are the same and the widthwise sides are the same (like a rectangle), use the equations P = 2a + 2b or P = 2(a + b)
