All solvers attempt to minimize an objective function. If you have a maximization problem, that is, a problem of the form
then define g(x) = –f(x), and minimize g.
For example, to find the maximum of tan(cos(x)) near x = 5, evaluate:
[x fval] = fminunc(@(x)-tan(cos(x)),5) Local minimum found. Optimization completed because the size of the gradient is less than the default value of the function tolerance. x = 6.2832 fval = -1.5574
fval), and occurs at x = 6.2832. This answer is correct since, to five digits, the maximum is tan(1) = 1.5574, which occurs at x = 2π = 6.2832.