On inverse permutation polynomials

We give an explicit formula of the inverse polynomial of a permutation polynomial of the form x^rf(x^s) over a finite field F"q where s|q-1. This generalizes results in [A. Muratovic-Ribic, A note on the coefficients of inverse polynomials, Finite Fields Appl. 13 (4) (2007) 977-980] where s=1 or f=g^q^-^1^s were considered respectively. We also apply our result to several interesting classes of permutation polynomials.