If I have two independent variables x,y, and two measurements, m1, m2 with errors. And the dependence is thus: [tex] m_1 \pm \delta m_1 = f[x,y] [/tex] [tex] m_2 \pm \delta m_2 = g[x,y] [/tex] Now in my case, f and g are complicated expressions of x and y with no simple solution. (Actually I think i can solve one for x, but not for y). Now if the equations were easy, I could solve for x and y: [tex] x \pm \delta_x = F[m_1, m_2,...] [/tex] [tex] y \pm \delta_y = G[m_1, m_2,...] [/tex] And from there add the errors in quadrature to get the x and y errors. BUT if I cant solve for x and y independently, and I must use numerical solutions to get the results ( I can, its easy). How can I go about getting the ERRORS? Is there another way I can solve for the errors and numerically solve for them, or a different method? I have Mathematica if that helps.