A polygon's perimeter depends both on its type and the number of sides it possesses. The relationship that a polygon's sides have with each other can divide a polygon into two different types, regular and irregular. Regular polygons must have sides with identical measurements, while irregular polygons have different-sized sides. While finding a regular octagon's perimeter means measuring just one side length and multiplying it by eight, finding an irregular polygon's perimeter means you must measure all sides separately.
Instructions
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1
Select one side of the octagon and measure it. For this example, let the side measure 3 inches.
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2
Measure the rest of sides rotating clockwise. In this example, let the other seven sides measure 3, 2.5, 2.5, 4, 5, 2 and 3 inches.
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3
Add the measurements together. Concluding this example, the sum of 3, 3, 2.5, 2.5, 4, 5, 2 and 3 inches is 25 inches. This is the irregular octagon's perimeter.