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EXAMPLE 1

a. Area. = π (2.5) 2. r = 2.5 cm. ANSWER. The area about 19.63 square centimeters. Use the formula for area of a circle. EXAMPLE 1. Find the indicated measure. SOLUTION. A = π r 2. Write formula for the area of a circle. Substitute 2.5 for r. = 6.25π. Simplify. ≈ 19.63.

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EXAMPLE 1

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  1. a. Area = π (2.5)2 r= 2.5 cm ANSWER The area about 19.63 square centimeters. Use the formula for area of a circle EXAMPLE 1 Find the indicated measure. SOLUTION A = πr2 Write formula for the area of a circle. Substitute 2.5 for r. = 6.25π Simplify. ≈ 19.63 Use a calculator.

  2. b. Diameter 113.1 = r2 π A = 113.1 cm2 ANSWER The radius is about 6 centimeters, so the diameter is about 12 centimeters. Use the formula for area of a circle EXAMPLE 1 Find the indicated measure. SOLUTION A = πr2 Write formula for the area of a circle. 113.1 = πr2 Substitute 113.1 for A. Divide each side by π. 6 ≈ r Find the positive square root of each side.

  3. Find the areas of the sectors formed by UTV. Because m UTV = 70°, mUV = 70° and mUSV = 360° – 70° = 290°. Find areas of sectors EXAMPLE 2 SOLUTION STEP 1 Find the measures of the minor and major arcs.

  4. mUV Area of small sector = πr2 360° 70° = π 82 360° Find areas of sectors EXAMPLE 2 STEP 2 Find the areas of the small and large sectors. Write formula for area of a sector. Substitute. ≈ 39.10 Use a calculator.

  5. 290° = π 82 360° ANSWER The areas of the small and large sectors are about 39.10 square units and 161.97 square units, respectively. mUSV Area of large sector = πr2 360° Find areas of sectors EXAMPLE 2 Write formula for area of a sector. Substitute. ≈ 161.97 Use a calculator.

  6. 1. Area of D = π (14)2 The area of Dis about 615.75 ft2. for Examples 1 and 2 GUIDED PRACTICE Use the diagram to find the indicated measure. SOLUTION A = πr2 Write formula for the area of a circle. Substitute 14 for r. = 196π Simplify. = 617.75 Use a calculator

  7. Because m FDE = 120, mFE = 120 and mFGE = 360 – 120 = 140. for Examples 1 and 2 GUIDED PRACTICE Use the diagram to find the indicated measure. 2. Area of red sector SOLUTION STEP 1 Find the measures of major arcs.

  8. mFE Area of red sector = π r2 360 120 = π 142 360 ANSWER The area of red sector is about 205.25 ft2. for Examples 1 and 2 GUIDED PRACTICE STEP 2 Find the area of red sector. Write formula for area of a sector. Substitute. = 205.25 Use a calculator.

  9. Because m FDE = 120, MFE = 120 and mFGE = 360 – 120 = 240. for Examples 1 and 2 GUIDED PRACTICE Use the diagram to find the indicated measure. 3. Area of blue sector SOLUTION STEP 1 Find the measure of the blue arc.

  10. mFEG Area of blue sector = π r2 360 240 = π 142 360 ANSWER Area of blue sector is about 410.50 ft2. for Examples 1 and 2 GUIDED PRACTICE STEP 2 Find the area of blue sector. Write formula for area of a sector. Substitute. = 410.50 ft2 Use a calculator.

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