LESSON Areas of Circles and Sectors 11 3

LESSON Areas of Circles and Sectors 11 -3 Honors Geometry Warm-up: Find the area. Today: • 11. 1 -2 Assignment • 11. 3 Instruction 20 16 30° 160 u 2

LESSON 11 -3 Areas of Circles and Sectors 11. 3 Areas of Circles and Sectors Objective: 1. Find areas of circles. 2. Find areas of sectors of circles. 3. Find areas of composites. Vocabulary: sector of a circle, segment of a circle, composite

LESSON 11 -3 Areas of Circles and Sectors A Vocabulary sector: a region of a circle bounded by 2 radii and an arc of the circle. B C D segment of a circle: a region of a circle bounded by a chord of the circle and its corresponding arc. B A C D

LESSON 11 -3 Areas of Circles and Sectors Find the area of a circle with a radius of 8 p. A = 64 π p 2

LESSON 11 -3 Areas of Circles and Sectors 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. Answer: The area of the cover is about 6082 square inches.

LESSON 11 -3 Areas of Circles and Sectors ALGEBRA Find the radius of a circle with an area of 45 square inches. A. 3. 8 in. B. 4. 5 in. C. 5. 7 in. D. 7. 6 in.

LESSON 11 -3 Areas of Circles and Sectors The green portion of C is arc AB written AB. m. AB = 90° sector ACB of C A Find the length of AB (Circumference of C) C D B Find the area of sector ACB (area of C)

LESSON 11 -3 Areas of Circles and Sectors Find the measure of the sector that has a central angle of 50° and a radius of 12’. A = 20π ft 2

LESSON 11 -3 Areas of Circles and Sectors If mÐDCG = 120° and DC = 24, find the length of DG and the area of sector DCG. length of DG = 16π u area of sector DCG = 192π u 2 D C G

LESSON 11 -3 Areas of Circles and Sectors 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? Answer: The area of one slice of pie is about 6. 36 square inches.

LESSON 11 -3 Areas of Circles and Sectors Area of a circle. A = πr 2 Area of a sector: Area of sector ACB = Area of a segment. (Area of ¤C) B A C D

LESSON 11 -3 Areas of Circles and Sectors Find the area of: a segment of a circle whose chord is 12” and the measure of the intercepted arc is 120°. the checkered region. 6’

LESSON 11 -3 Areas of Circles and Sectors Find the area of speckled regions: 3” 6 6 6

LESSON 11 -3 Areas of Circles and Sectors Assignment Due tomorrow: • 11. 3 P. 803 #19 -29 odd, 33 -39 odd, 40 -42, 46