WEBVTT

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Here is the problem: Find the arc length and sector area for a 90° sector of a circle with radius 10.

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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 90°.

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Sector area for 90°.

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So the answer is r equals 10, d equals 20, C equals 20pi approximately 62.83185307, A equals 100pi approximately 314.1592654; for 90°: arc length 5pi approximately 15.70796327, sector area 25pi approximately 78.53981634.

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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 314.1592654.