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SPI 6.4.4 I CAN identify parts of a circle. I CAN find the circumference and area of a circle. •Circle – named from the center point. •Radius – one endpoint at the center; the other endpoint on the circle •Diameter – a segment that passes through the center and has both endpoints on the circle •Chords – endpoints on the circle •Central angle – an angle with its vertex at the center. Diameter equals 2 radius OR Radius is half the diameter D = 2r OR Example: r = 5 in; d = ? D = 140 in; r = ? R= d/2 radius diameter the distance around a circle Pi = 3.14 = = The ratio C = a number close to 3. d C = ∏d OR C = 2∏r amount of surface covered A=∏r² OR Ex. r = 5 cm A= ∏xrxr 5 cm Find the circumference. 1)d = 50 m 2)r = 64 m Find the area. 3)11 in 4)16 cm Round to the nearest whole number. C = 5 cm Radius 0.8 cm A = 2 cm² Round to the nearest tenth. C = 4.7 cm A = 1.8 cm² Diameter 1.5 cm 518.1 ft 254.34 ft A. 9.42 in C. 200.96 in If the r = 7m, then d = _____, C = _____, and A = ______. d = 14m C = 44m A = 154m² If the d = 11.5 ft, then r = _____, C = _____, and A = ______. r = 5.75ft C = 36ft A = 104ft² Circumference 1.57 in Diameter ? d = 0.5 in