Circle Theorems Explorer

Drag points around the circle to explore fundamental circle theorems. Watch angles update in real-time and see the relationships come alive.

Theorem

Measurements

Angle 1 --
Angle 2 --
Relation --
Arc --

Circle Theorems Explained

Key Theorems

  • Inscribed Angle: An angle formed by two chords is half the central angle subtending the same arc
  • Central Angle: Angle at the center is twice the inscribed angle on the same arc
  • Semicircle: Any angle inscribed in a semicircle is a right angle (90°)
  • Tangent-Radius: A tangent to a circle is perpendicular to the radius at the point of contact
  • Cyclic Quadrilateral: Opposite angles sum to 180°

Formulas

  • Inscribed angle: θ = α/2 (where α is central angle)
  • Central angle: α = 2θ
  • Arc length: s = rθ (θ in radians)
  • Sector area: A = (1/2)r²θ
  • Chord length: c = 2r·sin(θ/2)

Applications

  • Navigation and surveying
  • Architecture and design
  • Computer graphics
  • Astronomy and orbital mechanics