reserve m,n for non zero Element of NAT;
reserve i,j,k for Element of NAT;
reserve Z for set;

theorem Th84:
for i,j being Nat
for f be PartFunc of REAL m,REAL
  st f is_partial_differentiable_up_to_order i,Z & j <= i
holds f is_partial_differentiable_up_to_order j,Z by XXREAL_0:2;
