theorem Th28: :: MIDSP_3:28

for n being Nat
for m being Nat of n
for RAS being ReperAlgebra of n
for W being ATLAS of RAS holds
( RAS is_semi_additive_in m iff for x being Tuple of (n + 1),W holds Phi (x +* (m,(Double (x . m)))) = Double (Phi x) )