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Here is the problem: Find the arc length and sector area for a 60° sector of a circle with radius 6.

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Find the radius, diameter, circumference and area of a circle from any one of them.

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Diameter.

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Circumference.

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Area.

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Arc length for 60°.

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Sector area for 60°.

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So the answer is r equals 6, d equals 12, C equals 12pi approximately 37.69911184, A equals 36pi approximately 113.0973355; for 60°: arc length 2pi approximately 6.283185307, sector area 6pi approximately 18.84955592.

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Every measurement of a circle follows from its radius. The circumference grows in proportion to the radius and the area in proportion to its square.

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C/d equals 3.141592654 equals pi.

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A equals C times r/2 equals 113.0973355.