function g = cond01( x)

h = 1e-8;

X1(1,1) = rosenbrock( [x(1,1) + h; x(2,1)]);
X1(2,1) = rosenbrock( [x(1,1) - h; x(2,1)]);

X2(1,1) = rosenbrock( [x(1,1); x(2,1) + h]);
X2(2,1) = rosenbrock( [x(1,1); x(2,1) - h]);

g(1,1) = (X1(1,1) - X1(2,1)) / (2*h);
g(2,1) = (X2(1,1) - X2(2,1)) / (2*h);

