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Cut-The-Knot-Action 11!

Author:Tim Brzezinski
Topic:Equilateral Triangles
Creation of this applet was inspired by a tweet from Alexander Bogomolny. How can you formally prove what this applet informally illustrates?

Quick (Silent) Demo

New Resources

  • Parallel lines, Transversals and Segments
  • Open Education 2026
  • רישום חופשי
  • The Coordinate Plane (Cartesian Plane)
  • General Polar Equation of Conics with Rotation (2)

Discover Resources

  • AP Calculus volume problems
  • Investigating Angles in a Triangle
  • Modul 10A_Zalimu_SMA Negeri 2 Baubau
  • Water-Air Refraction of Light
  • Dudeney: Choosing a Site in an Isosceles Estate

Discover Topics

  • Tangent Line or Tangent
  • Real Numbers
  • Right Triangles
  • Expected Value
  • Trigonometry
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