Original: JÃ nos Bolyai ( pronounced ) ( December 15 , 1802 â '' January 27 , 1860 ) was a Hungarian mathematician , known for his work in non-Euclidean geometry .
Simplified: JÃ nos Bolyai ( December 15 , 1802 â '' January 27 , 1860 ) was a Hungarian mathematician , known for his work in non-Euclidean geometry .