The three-chord lemma states that in the figure above,
 |
Three-Chord Lemma
See also
ChordExplore with Wolfram|Alpha
References
Price, H. E. "The Three-Chord Lemma." The Mathematics Teacher 87, 743, 1994.Referenced on Wolfram|Alpha
Three-Chord LemmaCite this as:
Weisstein, Eric W. "Three-Chord Lemma." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Three-ChordLemma.html