 Circles 9.3 Page 532 DiameterIs a segment that passes through the center of the circle and has endpoints on the circle. Segment AC is the diameter. D =

Presentation on theme: "Circles 9.3 Page 532 DiameterIs a segment that passes through the center of the circle and has endpoints on the circle. Segment AC is the diameter. D ="— Presentation transcript:

Circles 9.3 Page 532 DiameterIs a segment that passes through the center of the circle and has endpoints on the circle. Segment AC is the diameter. D = 2r Radius Is a segment with one endpoint on the center and the endpoint on the circle. Segment OB is called the radius. R = ½ d AC O B If the diameter is 18 inches, find the radius. R = ½ 18 in. R = 9 in. If the radius is 2 ½ ft, find the diameter. D = 2r D = 2(2.5 ft.) D = 5 feet

The circumference of a circle is the distance around it. Finding the circumference is similar to finding the perimeter of a polygon. The number is about 3.14 or 22/7. 1.4 m Find the circumference of the circle. Use 3.14 for pi. C = 3.14 (1.4 m) C = 4.396 m Now try a fraction for the Diameter.

3/4 m Find the circumference of the circle. Use 22/7 for pi. D = 2r ==

Find the perimeter of this figure. Use 3.14 for pi. 7.1 yd 3.2 yd 2 half circles make a whole circle. P = 7.1 + 7.1 + 3.14(6.4) 3.2 + 3.2 6.4 We need the Diameter. P = 7.1 + 7.1 + 20.096 P = 34.296 yd 20.296 7.1 + 7.1 34.296

Area of a circle page 535 The area of a circle with radius of length r is given by 14cm Find the area of the circle using 22/7 for pi. 28 A = 616 cm 2 28 x 22 56 560 616 3.14 x 196 1884 28260 31400 61544. Decimal point Using 3.14

Area of a circle page 535 The area of a circle with radius of length r is given by 5km Find the area of the circle using 22/7 for pi. 25 x 22 50 500 550 3.14 x 25 1570 6280 7850. Decimal point Using 3.14

The area of a circle with radius of length r is given by: 10.4 cm Find the area of the circle using 3.14 for pi. 10.4 x 10.4 416 0000 10816. A = (3.14)(10.4)(10.4 ) 10400 10816. x 3.14 43264 108160 3244800 3396224.

Which is larger and by how much: a l0 ft square flower bed or a 12 ft diameter flower bed? 10 ft 12 ft A = S x S A = 10 x 10 A = 100 sq ft r = 6 A = 113.04 sq ft 113.04 - 100.00 13.04 The 12 ft diameter flower bed is larger by

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