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Circle Theorems: Chords, Angles, and Cyclic Quadrilaterals

9th Grade · Math · Open Global Math

7 lessons

Goal

Prove circle theorems involving chords, central and inscribed angles, angles in the same segment, and cyclic quadrilaterals.

7 lessons
0 of 7 done
  1. Perpendicular Bisector of a Chord Theorem and ProofUp next
  2. Equidistant Chords and Chords of Equal LengthNot started yet
  3. Inscribed Angle Theorem and CorollariesNot started yet
  4. Circle Theorems: Angles in the Same SegmentNot started yet
  5. Angle in a Semicircle: Thales' Circle TheoremYou are here
  6. Circle Theorems: Cyclic QuadrilateralsNot started yet
  7. Converse: If Opposite Angles Are Supplementary, Points Lie on a CircleNot started yet
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Learning standards covered

GlobalOGM.10.GEO.4Open Global Math Standards 2026™ · 9th Grade

Investigate and prove circle theorems: perpendicular bisector of a chord, inscribed angle theorem and its corollaries, cyclic quadrilaterals, tangents and secants, and tangent segment lengths from an external point.