Nonlinear Equations Description The Nonlinear Equations module solves systems of nonlinear equations where there are as many equations as unknowns. The new version utilizes new GAUSS functions, significantly increasing accuracy and computational speed. The functions must be continuous and differentiable. You may provide a function for calculating the Jacobian, if desired. Otherwise NLSYS will compute the Jacobian numerically. You can also select from two descent algorithms, the Newton method or the Secant Update method, and from two step-length methods, a quadratic/cubic method, or the hookstep method. Platform: Windows, LINUX and UNIX. Requirements: GAUSS/GAUSS Light version 3.2 or higher.