Ideal one dimensional MHD (non-resistive) equations are used to study the rotational instability in field reversed configuration plasmas. Instead of using resistive boundary layer analysis, the eigenmode non hermitian equations are solved on the complex w-plane using a numerical code constructed using "Mathematica". We take into account the plasma compressibility and compare our results with the Compact Torus (TC-1) experiment of the Universidade Estadual de Campinas (UNICAMP), which is presented here. The m = 4 rotational mode observed in TC-1 is used to verify the consistency of our model.