:: deftheorem defines is_partial_differentiable_on PDIFF_9:def 12 :
for m being non zero Element of NAT
for Z being set
for i being Element of NAT
for f being PartFunc of (REAL m),REAL holds
( f is_partial_differentiable_on Z,i iff f is_partial_differentiable_on Z,<*i*> );