A new proof for the Erdős-Ko-Rado theorem for the alternating group

A subset S of the alternating group on n points is intersecting if for any pair of permutations π,σ in S, there is an element i∈{1,…,n} such that π(i)=σ(i). We prove if n≥5 and S is intersecting, then |S|≤(n−1)!2. Also, we prove that provided that n≥5, then the only sets S that meet this bound are the cosets of the stabilizer of a point of {1,…,n}. These two results were first proven by Ku and Wong (2007), the proof given in this paper uses an algebraic method that is very different from the original proof.