The solution of sets of non-linear partial differential equations using the method of integral relations is considered. Emphasis is laid on the derivation of a general N-strip approximation algorithm. In order to check the applicability of this algorithm a program has been written to obtain the solution of the flow field around a circular cone at incidence in supersonic flow. Using the method of Stone, the angle of attack has been taken into account up to the second order. Thus a comparison can be made with the results given by Kopal. The results show that the N-strip algorithm in the case studied is a very attractive method which leads straight-forward to results of high accuracy.