Let q ≥ 3 be a prime and let H (λ q ) be the Hecke group associated to q. Let m be a positive integer and H m (λ q ) be the mth power subgroup of H (λ q ). In this work, we study the commutator subgroups of the power subgroups H m (λ q ) of H (λ q ). Then, we give the derived series for all triangle groups of the form (0; 2, q, n) for n a positive integer, since there is a nice connection between the signatures of the subgroups we studied and the signatures of these derived series.