Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.



Published on

Published in: Education
  • Login to see the comments


  1. 1. Area of Circlesand Partsof Circles
  2. 2. Radius• The radius of a circle is from the center to the outer edge of the circle.• The radius is one half of the diameter as shown here. r
  3. 3. Diameter• The diameter goes A from one edge of the circle to the C D other.• The diameters is twice the radius or B r2. m CD = 2.17 cm• AB
  4. 4. Pi π• Pi is ≈ 3.14• Pi is represented by the symbol π
  5. 5. Parts of a circle A In circle O, OB is a radiusO AC is a diameter BC
  6. 6. Parts of a circle A The distance around circle O is called theO circumference of B the circle. It is similar to the perimeter of aC polygon.
  7. 7. The number π A The ratio of the circumference of O a circle to its diameter is the number π. m CA = 5.8982 cm CCircumference OB = 18.5299 cm(Circumference OB) = 3.1416 m CA
  8. 8. Finding the Circumference Since we know d that C/d = π we can solve for C. r C (d ) = π(d) dTherefore: C = π d or C = 2π r
  9. 9. PracticeFinding the Circumference d = 46 cm d Find the r circumference. C = 46π cm or 144.51 cm
  10. 10. PracticeFinding the Circumference d = 2.8 m d Find the r circumference. C = 2.8π m or 8.80 m
  11. 11. PracticeFinding the Circumference r = 18 cm d Find the r circumference. C = 36π cm or 113.10 cm
  12. 12. Finding the area of a circle The area of a circle is found r using the formula A = πr2
  13. 13. Practice Finding the area of a circle A A = πr2 C D A = π(2.17)2 A = 4.7089π cm 2 B or 14.79 cm 2m CD = 2.17 cm
  14. 14. PracticeFinding the area of a circle A A = πr2 C D A = π(5.19/2)2 A = 6.734π cm2 Bm AB = 5.19 cm or 21.16 cm2