Consider that one has several functions, say 3, of the form f(x,y,z) and g(x,y,z) and h(x,y,z). You know the form of these equations and they are non-linear, long, messy equations. f', g' and h' are even longer and messier and therefore assume that they cannot be found.

Now consider you measure f, g and h and want to determine x, y and z.

What method is recommended for solving this in a numerical and computationally efficient (but simple to implement) manner?

Cheers,

Natski