  The closed analytical expression for the electron density of states function
in a rectangular lattice is derived in an elementary way in terms of complete
elliptic integrals of the first kind. The lattice can be treated as a deformed
square lattice under uniform uniaxial stress (or strain). In contrast to
hydrostatic case the uniaxial pressure, say along axis y, modifies a length of
the y-bonds while the x-bonds remain intact. It also alters the corresponding
tight-binding transfer integral gamma_2 between two y-nearest-neighbours
leaving unchanged the gamma_1 for x-nn interactions. Due to stress-induced
lowering symmetry of this simple model one can get an insight into the
decoupling of its density of states on dependence of the lattice deformation or
transfer integrals anisotropy.
