Then B N is a strict normal subgroup of B . Let us consider G , let N be a normal subgroup of G , and let us consider B . Then N B is a strict normal subgroup of B . Let G be a non empty 1-sorted structure. Let us observe that there exists a group which is trivial.
G is trivial.
G is finite. Let us consider G , N . Let us consider G , N . Note that Cosets N is non empty. For every normal subgroup N of G holds a N Cosets N and N a Cosets N .