Finite element approximation to a model problem of transonic flow

A model problem of transonic flow ''the Tricomi equation'' in Ω is contained in IR2 bounded by the rectangular-curve boundary is posed in the form of symmetric positive differential equations. The finite element method is then applied. When the triangulation of Ω-bar is made of quadrilaterals and the approximation space is the Lagrange polynomial, we get the error estimates. 14 refs, 1 fig