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Circumference
📖 Perimeter Study Guide
5. Circumference and Sectors
The perimeter of a circle has a special name: circumference. It is the distance around the outside of the circle.
• The radius () is the distance from the center to any point on the boundary.
• The diameter () is the distance across the circle through the center ().
• The radius () is the distance from the center to any point on the boundary.
• The diameter () is the distance across the circle through the center ().
To calculate the circumference, we use:
Perimeter of a Sector
A sector is a slice of a circle (like a pizza slice). The boundary of a sector consists of two straight radii and one curved arc.
By adding the two straight radius sides () and the curved arc, the total perimeter formulas are:
By adding the two straight radius sides () and the curved arc, the total perimeter formulas are:
• In Radians (central angle ):
• In Degrees (central angle ):
Learning Topics
Frequently Asked Questions
How do you find the perimeter of a right-angled triangle if one side is missing?
Since we've already learned the Pythagorean theorem (a² + b² = c²), we can calculate the missing side length first and then sum all three sides together to get the perimeter.
What is perimeter?
Perimeter is the total boundary of a two-dimensional shape. It includes both the outer boundary and any inner boundaries (like the edges of holes inside the shape).