N geometryThales' theorem (named after Thales of Miletus) states that if A, B and C are points on a circle where the line AC is a diameter of the circle, then the angle ∠ABC is a right angle. Thales' theorem is a special case of the inscribed angle theorem, and is mentioned and proved on the 33rd proposition, third book of Euclid's Elements. It is generally attributed to Thales, who is said to have offered an ox (probably to the god Apollo) as a sacrifice of thanksgiving for the discovery, but sometimes it is attributed to Pythagoras.
If a line is parallel to the 1 side of triangle and intersects 2 other sides at different points then the intercepts made are in proportion. This is also called Basic Proportionality theorem.
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