Steiner–Lehmus theorem

The set of Steiner Lehmus is a set of elementary geometry about triangles. He was first formulated by Christian Ludolf Lehmus and then proved by Jakob Steiner.

The phrase was first mentioned in 1840 in a letter from CL Lehmus to Charles -François Sturm, in which this C. tower asked for an elementary geometric proof of the statement. C. Sturm widespread the problem under other mathematicians and Jakob Steiner was one of the first who provided a proof. Since then, the rate has been published to a popular subject of elementary geometry to the numerous publications in the following 160 years.