theorem :: PDIFF_3:1

for x0, y0 being Real
for z being Element of REAL 2
for f being PartFunc of (REAL 2),REAL st z = <*x0,y0*> & f is_hpartial_differentiable`11_in z holds
SVF1 (1,(pdiff1 (f,1)),z) is_differentiable_in x0