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Section 7-7: Circles: Area of circles, sectors, and segments. April 10, 2012. Warm-up: (20 mins). Create your own figure using a circle and at least 2 other types of shapes. Include at least 5 shapes. Swap with your partner. Find the perimeter/circumference of the figure.
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Section 7-7: Circles: Area of circles, sectors, and segments April 10, 2012
Warm-up: (20 mins) • Create your own figure using a circle and at least 2 other types of shapes. Include at least 5 shapes. • Swap with your partner. • Find the perimeter/circumference of the figure. • Check each other’s work.
Section 7-7 Circles: Area of circles, sectors, and segments • Objective: Today you will learn to find areas of • circles • sectors • segments
Area of a Circle • Area of a parallelogram = b*h = ½ C*r • C = 2πr Area of a circle = ½ (2πr)*r = πr2 • Area of our cookie cake is ____________.
Example 1: Find the exact area of these circles Example 2: What is the radius of a circle with area = 144πm2?
Area of a Sector:How big is your piece of the pie? • Sector – region bounded by two radii and their intercepted arc • Area of sector = * area of circle
Example 4: Find area of sectors with the given information: a) mXY = 720; r = 20cm b) mMN = 1200; r = 6 ft c) mAB = 1500; d = 8 in
Example 5: Find areas in terms ofπ Circle A = Sector CD = Sector DEC = Sector CDE = Sector ED = Sector CD + Sector DEC =
Segment of a circle Segment of a circle– region of a circle bounded by an arc and the segment joining its endpoints
Area of a Segment of a circle Area of sector - Area of triangle = Area of segment
Example 6: Find area of shaded segment. Round your answer to the nearest tenth.
Example 7: Find area of shaded segment. Round your answer to the nearest tenth.
Example 7 (cont’d): Find area of shaded segment. Round your answer to the nearest tenth.
Example 7 (cont’d): Find area of shaded segment. Round your answer to the nearest tenth.
Example 8: Find area of shaded segment. Round your answer to the nearest tenth.
Example 9: Find area of shaded segment. Round your answer to the nearest tenth.
Example 10: Find area of shaded segments. Round your answer to the nearest hundredth. • Given: • AD = 8√3 • m∠AEF = 600
Wrap-up • Today you learned to find areas of • circles • sectors • segments • Tomorrow you will learn about Geometric Probability Homework (H) • p. 397 # 1 - 11, 17 – 19, 22, 23, 25, 27, 32, 35 Homework (R) • p. 397 # 1 - 11, 17 – 19, 22, 25, 26, 27, 28, 35