Sufficient conditions for which a
minimal graph over a nonconvex domain is area-minimizing are presented. The
conditions are shown to hold for subsurfaces of Enneper’s surface, the singly periodic
Scherk surface, and the associated surfaces of the doubly periodic Scherk surface
which previously were unknown to be area-minimizing. In particular these surfaces
are graphs over (angularly accessible) domains which have a nice complementary set
of rays. A computer assisted method for proving polynomial inequalities with rational
coefficients is also presented. This method is then applied to prove more general
inequalities.