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

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

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

4. EXAMPLE 2 STEP 2 Find the areas of the small and large sectors. Area of small sector = πr 2 m UV 360 ° Write formula for area of a sector. = π 8 2 70 ° 360 ° Substitute. ≈ 39.10 Use a calculator. Find areas of sectors

5. EXAMPLE 2 = π 8 2 290 ° 360 ° Substitute. ≈ 161.97 Use a calculator. Find areas of sectors The areas of the small and large sectors are about 39.10 square units and 161.97 square units, respectively. ANSWER Area of large sector = πr 2 m USV 360 ° Write formula for area of a sector.

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

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

8. GUIDED PRACTICE for Examples 1 and 2 Write formula for area of a sector. = π 14 2 120 360 Substitute. = 205.25 Use a calculator. Area of red sector = π r 2 m FE 360 The area of red sector is about 205.25 ft 2. ANSWER STEP 2 Find the area of red sector.

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

10. GUIDED PRACTICE for Examples 1 and 2 Area of blue sector = π r 2 m FEG 360 Write formula for area of a sector. = π 14 2 240 360 Substitute. = 410.50 ft 2 Use a calculator. Area of blue sector is about 410.50 ft 2. ANSWER STEP 2 Find the area of blue sector.