1 / 16

The circumference and Area of a circle

The circumference and Area of a circle. http://hench-maths.wikispaces.com. What is the formula relating the circumference to the diameter?. circumference. centre. Diameter. Radius. C = ? x d.

sandra_john
Download Presentation

The circumference and Area of a circle

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. The circumference and Area of a circle http://hench-maths.wikispaces.com

  2. What is the formula relating the circumference to the diameter? circumference centre Diameter Radius

  3. C = ? x d People knew that the circumference is about 3 times the diameter but they wanted to find out exactly. C ≈ 3 x d This means APPROXIMATELY EQUAL TO

  4. Investigating the relationship between the circumference of a circle and its diameter? Click on the link below and read the instructions. Use the applet to create circles with different diameters. Roll the circles on the number line to measure the circumference. Your goal is to discover the mystery number in the formulae by dividing the circumference by the diameter for each circle. If you measure and divide corectly you should always get the same value for the ratio circumference/diameter http://arcytech.org/java/pi/measuring.html

  5. The mystery ratio • What value did you find for the ratio? 3.1-3.2 is pretty good 3.14 is very good and close to the true value For most circumstances we say Circumference ≈ 3.14 x diameter What is the true value of this mystery ratio?????

  6. Early Attempts Egyptian Scribe Ahmes. in 1650 B.C. said C≈3.16049 x d Archimedes, said C ≈3.1419 x d Fibonacci. In 1220 A.D. said C≈3.1418xd What is the value of the number that multiplies the diameter to give the circumference????

  7. The exact true value is…………… UNKNOWN!!

  8. An approximation to π π≈3.141592653589793238462643383279502884197169399375105820974944592307816406286208998628034825342117067982148086513282306647093844609550582231725359408128481117450284102701938521105559644622948954930381964428810975665933446128475648233786783165271201909145648566923460348610454326648213393607260249141273724587006606315588174881520920962829254091715364367892590360011330530548820466521384146951941511609................forever….

  9. Videos on Circles • http://www.youtube.com/watch?v=eiHWHT_8WrE • A Rap about circles http://www.youtube.com/watch?v=fogehnFNDw0&feature=related • Circle Song2 http://www.youtube.com/watch?v=lWDha0wqbcI&feature=related

  10. What about the AREA of a circle? 2r First consider a square The area of this square in terms of r is A= 2r x2r = 4r2 r 2r

  11. What about the AREA of a circle? Now consider a circle inside the square The area of the circle must be less than the are of the square A < 4r2 2r r 2r Area = ? xr2

  12. Finding a formulae for the area of a circle

  13. C= πd or C=2πr Semi-circle=πr πr r

  14. Area of Rectangle= Base x Height Area = πr x r Area =πr2

  15. A circle is defined by its diameter or radius The Area and Perimeter of a Circle The perimeter or circumference of a circle is the distance around the outside radius The area of a circle is the space inside it Diameter The ratio of π (pi) The circumference is found using the formula C=π d or C= 2πr (since d=2r) The area is found using the formula A=πr2

  16. A circle is defined by its diameter or radius The Area and Perimeter of a Circle The perimeter or circumference of a circle is the distance around the outside radius The area of a circle is the space inside it Diameter The ratio of π (pi) The circumference is found using the formula C=π d or C= 2πr (since d=2r) The area is found using the formula C=πr2

More Related