for f being PartFunc of COMPLEX,COMPLEX
for u, v being PartFunc of (REAL 2),REAL
for z0 being Complex
for x0, y0 being Real
for xy0 being Element of REAL 2 st ( for x, y being Real st x + (y * <i>) in dom f holds
( <*x,y*> in dom u & u . <*x,y*> = (Re f) . (x + (y * <i>)) ) ) & ( for x, y being Real st x + (y * <i>) in dom f holds
( <*x,y*> in dom v & v . <*x,y*> = (Im f) . (x + (y * <i>)) ) ) & z0 = x0 + (y0 * <i>) & xy0 = <*x0,y0*> & f is_differentiable_in z0 holds
( u is_partial_differentiable_in xy0,1 & u is_partial_differentiable_in xy0,2 & v is_partial_differentiable_in xy0,1 & v is_partial_differentiable_in xy0,2 & Re (diff (f,z0)) = partdiff (u,xy0,1) & Re (diff (f,z0)) = partdiff (v,xy0,2) & Im (diff (f,z0)) = - (partdiff (u,xy0,2)) & Im (diff (f,z0)) = partdiff (v,xy0,1) )