1. The problem statement, all variables and given/known data[/prove f(x1,y1)-f(x0,y0)=fx(x*,y*)(x1-x0)+fy(x*,y*)(y1-y0) prove there exists a point (x*,y*) if fx and fy are all continuous on a circular region and contain A(x0,y0) and B(x1,y1) 2. Relevant equations 3. The attempt at a solution I'm thinking mean value theorem but honestly i have no idea how to do this. i dont even know how to properly apply the mean value theorem to this since there are two variables changing and the teacher said something about parametrization.