for x being set
for V being RealLinearSpace
for Affv being finite affinely-independent Subset of V
for EV being Enumeration of Affv
for A being Subset of V st A c= Affv & x in Affin Affv holds
( x in Affin A iff for y being set st y in dom (x |-- EV) & not EV . y in A holds
(x |-- EV) . y = 0 )