What is Thales's theorem?
[[File:Thales's_theorem_diagram.png|thumb|A graph demonstrating Thales's Theorem.]] '''Thales's theorem''' is a [[theorem]] (rule) in [[geometry]]. It says that if three [[Point (geometry)|points]], <math>P</math>, <math>Q</math>, and <math>R</math> are on a [[circle]] where <math>PR</math> is a [[diameter]] (a straight line from one end of the circle to another, through the middle), the angle <math>PQR</math> is a [[right angle]] of 90 degrees. This is a special case of the [[Inscribed angle|inscribed angle theorem]]. {{math-stub}} [[Category:Theorems in geometry]] [[Category:Angles]]