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Circles

Circles. A Circle is a closed plane figure in which all the points are the same distance from the center. Center. F. Circle F. Chords: AB AC AD. A Chord is a line segment that connects two points on a circle. B. C. Y. A. D. Diameter: AC.

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Circles

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  1. Circles

  2. ACircleis a closed plane figure in which all the points are the same distance from the center. Center F Circle F

  3. Chords: AB AC AD AChordis a line segment that connects two points on a circle. B C Y A D

  4. Diameter: AC The Diameterof a circle is a special chord that passes through the center of a circle. B C E A D

  5. Radii: YA YC YD (plural form of radius) The Radiusof a circle is a line segment from the center of the circle to any other point on the circle. B Y C A D

  6. The length of the radius is one half the length of the diameter. diameter radius d = 2 x r or r = d ÷ 2 d (diameter) r (radius) If r = 2 cm, then d = 4 cm. If d = 5 in, then r = 2.5 in.

  7. P You can use a compass to construct a circle. Step 1: Open the compass to the length of the radius. Step 2: Put the tip of the compass at a point to be the center. Step 3: Rotate the pencil around the center. compass

  8. The Circumferenceis the distance around a circle. C (circumference) circumference

  9. The Circumferenceof a circle is greater than its diameter. It is always the same number of times as great. This number is called piand is represented by the symbol π. ( π  3.14) You can find the circumference by multiplying π times the diameter. ( C = π x d )

  10. 8 cm E G F d = 8 cm C = π x d = 3.14 x 8 = 25.12 cm The circumference is 25.12 cm.

  11. 3 in S T r = 3 in Remember: d = 2 x r C = π x d C = 2 x π x r = 2 x 3.14 x 3 = 18.84 in The circumference is 18.84 in.

  12. C = 62 m Find the diameter (d) to the nearest hundredth. C = π x d diameter 62 = 3.14 x d 62 ÷ 3.14 = d d = 19.75 The diameter is 19.75 m.

  13. C = 52 in Find the radius (r) to the nearest hundredth. radius C = π x d C = 2 x π x r 52 = 2 x 3.14 x r 52 = 6.28 x r r = 52 ÷ 6.28 The radius (r) is 8.28 in.

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