This paper deals with the geometry of strain superposition in two dimensions. Four models of homogeneous deformations are considered: body rotation, simple shear, pure shear and area change. Each model is properly described by a 2x2 matrix, and the sequential superposition of two or more deformations is adequately analyzed by the matrix multiplication. The finite state of strain is described in terms of the total strain, and from that, several mathematical expressions are obtained, e.g., the strain ellipse equation, the change in length of a line, the change in the angle between two lines, the change in area, the ratio of the principal strains and the orientations, rotations and magnitudes of the principals strains axes. The applications of these equations depend on the correct data that can be obtained from geological maps, sections or samples and others informations that can be directly obtained from rock exposures and thin sections. The results may be used to restore deformed sections to an undeformed state.
