FMINCON is part of the commercial Optimization Toolbox from Mathworks.
FMINCON is invoked with sdpsettings('solver','fmincon').
FMINCON is used as a general purpose nonlinear solver, and in particular used as an upper bound solver when solving nonconvex problems using BMIBNB, or lower bound solver when solving mixed-integer problems using BNB.
FMINCON can also be used by YALMIP to solve geometric programming problems. In these cases, YALMIP automatically performs the standard convexifying variable change and solves the convex problem instead. To explicitly tell YALMIP to try to perform this conversion, use the tag 'fmincon-geometric'. To tell YALMIP not to try to find a geometric program, use 'fmincon-standard' and YALMIP will simply try to solve the problem in the original variables.