The Geometry of Circles
Definitions and formulas for the radius of a circle, the diameter of a circle, the circumference (perimeter) of a circle, the area of a circle, the chord of a circle, arc and the arc length of a circle, sector and the area of the sector of a circle
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| radius of a circle | diameter of a circle | circumference of a circle |
| area of a circle | chord of a circle | arc of a circle |
| arc length of a circle | sector of a circle | area of a sector of a circle |
| The radius of a circle: | |
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The radius of a circle is the distance from the center of the circle to the outside edge. |
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| The diameter of a circle: | |
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The diameter of a circle is longest distance across a circle. (The diameter cuts through the center of the circle. This is what makes it the longest distance.) |
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| The circumference of a circle (the perimeter of a circle): | |
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The circumference of a circle is the perimeter -- the distance around the outer edge. Circumference = |
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| The area of a circle: | |
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Area = |
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| A chord of a circle: | |
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A chord of a circle is a line segment that connects one point on the edge of the circle with another point on the circle. (The diameter is a chord -- it's just the longest chord!) |
