EXAMPLE 1
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Transcript of EXAMPLE 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 = πr2
The area of A is about 19.63 square centimeters.
ANSWER
EXAMPLE 1 Use the formula for area of a circle
Find the indicated measure.
A = 113.1 cm2
b. DiameterWrite formula for the area of a circle.
Substitute 113.1 for A.113.1 = πr2
= r2113.1π
Divide each side by π.
6 ≈ r Find the positive square root of each side.
The radius is about 6 cm, so the diameter is about 12 centimeters.
ANSWER
A = πr2
SOLUTION
EXAMPLE 2 Find areas of sectors
Find the areas of the sectors formed by UTV.
SOLUTION
STEP 1Find the measures of the minor and major arcs.
Because m UTV = 70°, mUV = 70° and mUSV = 360° – 70° = 290°.
EXAMPLE 2
STEP 2
Find the areas of the small and large sectors.
Area of small sector = πr2
mUV360°
Write formula for area of a sector.
= π 8270°
360°Substitute.
≈ 39.10 Use a calculator.
Find areas of sectors
EXAMPLE 2
= π 82290°
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
Write formula for area of a sector.
Area of large sector = πr2 mUSV360°
GUIDED PRACTICE for Examples 1 and 2
1. Area of D
Use the diagram to find the indicated measure.
about 615.75 ft2ANSWER
GUIDED PRACTICE for Examples 1 and 2
2. Area of red sector
Use the diagram to find the indicated measure.
about 205.25 ft2ANSWER
GUIDED PRACTICE for Examples 1 and 2
3. Area of blue sector
Use the diagram to find the indicated measure.
about 410.50 ft2.ANSWER