Dear Forum, Is it the case to find a presentation of the derived subgroup of the following Hecke groups in GAP using Reidemeister-Schrier Method? There are information in manuals but I think I need to see an application: Let q\geq 3 be an integer and H_q=< x,y: x^2=y^q=1> . Best wishes, Ahmet Arıkan iPad'imden gönderildi