# 11-3 Areas of Circles and Sectors You found the circumference of a circle. Find areas of circles....

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11-3 Areas of Circles and SectorsYou found the circumference of a circle. Find areas of circles.Find areas of sectors of circles.

Area of a CircleThe formula for area of a circle is:

A = r2A = arear = radius

p. 798

If the radius of C is 3 cm, what is its area? Answer in exact form.A = r2A = 32A = 9

MANUFACTURING An outdoor accessories company manufactures circular covers for outdoor umbrellas. If the cover is 8 inches longer than the umbrella on each side, find the area of the cover in square inches.The diameter of the umbrella is 72 inches, and the cover must extend 8 inches in each direction. So, the diameter of the cover is 8 + 72 + 8 or 88 inches. Divide by 2 to find that the radius is 44 inches.Answer:The area of the cover is about 6082 square inches. Area of a circle Substitution Use a calculator.

A.62.8 ft2B.254.5 ft2C.314.2 ft2D.1256.6 ft2A swimming pool company manufactures circular covers for above ground pools. If the cover is 1 foot longer than the pool on each side, find the area of the cover.

If the area of C is 49, what is its diameter?A = r249 = r2 49 = r2r = 7

ALGEBRA Find the radius of a circle with an area of 58 square inches.Answer:The radius of the circle is about 4.3 in.Area of a circleSubstitutionDivide each side by .Simplify.4.3 r

A.3.8 in.B.4.5 in.C.5.7 in.D.7.6 in.ALGEBRA Find the radius of a circle with an area of 45 square inches.

The South Rose window in Notre Dame has a diameter of 12.9 meters. Find the area and circumference of the window.A = r2A = (12.9)2A = 166.41 A = 522.79 meters2C = 2rC = 2(12.9)C = 25.8C = 81.05 meters

If the area of M is 121 m2, find its circumference.A = r2121 = r2 38.5 = r2r = 6.2 mC = 2rC = 2(6.2)C = 38.99 mMWhat letter is common to both the area and circumference formulas?r (radius)

Sector AreaSector area is the wedge-shaped interior regions of a circle formed by central angles.

A sector of a circle is a region formed by two radii and an arc of circle. ABC is a sector of BABC

Formula for Sector Lengthp. 799

is a central angle of KThe arc covers 125 out of a total of 360 orFind the area of sector JKL to the nearest tenth.

PIE A pie has a diameter of 9 inches and is cut into 10 congruent slices. What is the area of one slice to the nearest hundredth? Step 1Find the arc measure of a pie slice.Since the pie is equally divided into 10 slices, each slice will have an arc measure of 360 10 or 36.Step 2Find the radius of the pie. Use this measure to find the area of the sector, or slice.The diameter is 9 inches, so the radius is 4.5 inches.Area of a sectorx = 36 and r = 4.5Use a calculator.Answer:The area of one slice of pie is about 6.36 square in.

A.16.21 in2B.19.24 in2C.26.43 in2D.38.48 in2PIZZA A pizza has a diameter of 14 inches and is cut into 8 congruent slices. What is the area of one slice to the nearest hundredth?

11-3 AssignmentPage 801, 8-22 even

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