GeoGebra
  • Create Lesson
GeoGebra
  • Home
  • News Feed
  • Resources
  • Profile
  • People
  • Classroom
  • App Downloads
About GeoGebra
Contact us: office@geogebra.org
Terms of Service – Privacy – License

© 2022 GeoGebra

Surprising Annulus Area Result

Author:
Jennifer Silverman
Topic:
Area
Alex Cutbill's Observation: To find the area of an annulus (the region between two concentric circles) it's enough to know the length of the chord of the bigger circle which is tangent to the smaller circle.
Try moving D and E. Watch what happens. Now move P. I think this is what surprised Alex!

New Resources

  • Monty Hall Problem
  • Transformations
  • Action/Consequence Parallel Lines and Angles
  • G_8.04 Solving right triangles
  • Silky Pattern Generator

Discover Resources

  • material-2110313fixedBetter
  • material-2653537orig
  • Hexagon
  • รูปสามมิติจากกราฟของฟังก์ชัน
  • Temporizador: suma de enteros

Discover Topics

  • Addition
  • Volume
  • Similarity Transformation or Similarity
  • Prism
  • Hypothesis Testing

GeoGebra

  • About
  • Partners
  • GeoGebra on Tests
  • News Feed
  • App Downloads

Apps

  • Calculator Suite
  • Graphing Calculator
  • 3D Calculator
  • CAS Calculator
  • Scientific Calculator

Resources

  • Classroom Resources
  • Learn GeoGebra
  • Classroom
  • Geometry
  • Notes
  • Terms of Service Privacy License
  • Facebook Twitter YouTube