ASKSAGE: Sage Q&A Forum - RSS feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Sat, 05 Jan 2013 11:24:24 +0100Check whether a modular subgroup is congruence from its generatorshttps://ask.sagemath.org/question/9691/check-whether-a-modular-subgroup-is-congruence-from-its-generators/I want to input the generators of a specific subgroup of the modular group $\Gamma = PSL(2,\mathbb{Z})$ as explicit $2\times 2$ matrices, and have Sage tell me whether that subgroup is congruence. Clearly I need to use the command `is_congruence()` for the second part, but I'm having trouble inputting the subgroup generators. Potentially it is something very simple - can anyone help? Thanks.JimereeSat, 05 Jan 2013 11:24:24 +0100https://ask.sagemath.org/question/9691/