 Consider the subgroupsformula_25 of formula_26for some field formula_27.Then, the group quotient formula_28 can be found by taking arbitrary elements in formula_29, multiplying them together, and figuring out what structure this gives.Soformula_30Note the determinant condition on formula_31 implies formula_32, hence formula_33 is a subgroup (which are the matrices where formula_34).