Past exam of the mathematics course of the University of Cambridge 2020 ia Paper 2 6E b Solution Created 2026-09-24 Updated 2026-09-29
For the rotation group , the identity fixes all colorings. Because five is prime, each of the four nonidentity rotations is a single five-cycle and fixes exactly the constant colorings. Burnside lemma therefore gives the number of coloring necklaces
For the dihedral group , the five reflections each fix one vertex and interchange two pairs of vertices, so each fixes colorings. Adding these to the identity and rotation contributions gives the number of coloring bracelets