u know when the proof for c. presented here first appeared? 1880
Journal de mathematiques elementaires et speciales, 1880, p. 538
also attached are 3 articles on c.
Hajja, M., A Short Trigonometric Proof of the Steiner-Lehmus Theorem, Forum Geometricorum Volume 8 (2008) 39–42.
Sauvé, L...