Circles

Mr Elliott


  • 1. Circumference of Circles
  • 2. Area of Circles
  • 3. Exploring the Equation of a Circle
  • 4. Circle with Center and Radius
  • 5. Property of a tangent
  • 6. Definition of Tangent
  • 7. Rolling Coin 滾動的硬幣
  • 8. circle theorem 1a
  • 9. Radius perpendicular bisector of chord
  • 10. Circles & Their line segments
  • 11. Circle Theorem 1 - Angle at the Centre
  • 12. Circle Theorem 2 - Angles in a Semicircle
  • 13. Circle Theorem 3 - Angles in the Same Segment
  • 14. Circle Theorem 4 - Cyclic Quadrilateral
  • 15. Circle Theorem 5 - Radius to a Tangent
  • 16. Circle Theorem 6 - Tangents from a Point to a Circle
  • 17. Circle Theorem 7 - Tangents from a Point to a Circle II
  • 18. Circle Theorem 8 - Alternate Segment Theorem
  • 19. Area of Circles
  • 20. Area of a Circle - Wedge/Sector Demonstration
  • 21. Sine and Cosine Components

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Circumference of Circles

(See http://www.geogebratube.org/material/show/id/8222 for anothernew version.)[br][br]Drag the green point to appropriate position to measure the diameter of the circle.[br]Drag the red point P to straighten the circumference. Divide the scale of the ruler to measure its length to [b]two decimal places[/b]. Use the Zoom In, Zoom Out and Move tools if necessary.[br][br]Calculate the values of c/d. What do you discover?
Circumference of Circles
Anthony OR. GeoGebra Institute of Hong Kong.
– Anthony OR 柯志明

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