Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2018/ib/paper-4/2g/b/solution

Let , the symmetry group of a square. The map
preserves the relations and is an automorphism. Conjugation by a rotation sends to , while conjugation by a reflection also inverts . Therefore no conjugation fixes and sends to . This is an outer automorphism of the nonabelian group .

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