Prove that every non-trivial normal subgroup H of A5 contains a 3 -cycle. (Hint: The 3 -cycles are the non-identity ele
Posted: Wed Jul 13, 2022 5:10 am
Prove that every non-trivial normal subgroup H of A5 contains a 3 -cycle. (Hint: The 3 -cycles are the non-identity elements of A5 with the largest number of fixed points. If σ∈Sn, a reasonable way of trying to construct a permutation out of σ with more fixed points than σ is to form a commutator [σ,τ]=στσ−1τ−1 for an appropriate permutation τ∈Sn. This idea is used in the solution of Rubik's cube. Why is this a reasonable thing to try?)