A theoretical and computational check of the applied Yang Lee theorems to the Ising model was performed for a chain of spins and a square lattice of spins. It is possible to verify analytically and graphically that in the Ising model in one dimension there is no there are phase transitions, while for the two-dimensional model it was possible to verify graphically that if there is a phase transition around x=\exp(2J / K Tc) = 0.1715 as reported in the literature.