This means that rotation by 360˚/n and -360˚/n are equivalent. In other words a rotation C^ nm and its inverse C^ n-m belong to the same conjugate class when a mirror plane contains the rotation axis. For example, the operations of a C7 axis fall into the classes (C7, C76); (C72, C75); (C73, C74) and for a C6 axis the classes are (C6, C65); (C3, C32); (C2) when a sv or sd mirror plane also exists.