theorem :: RLAFFIN2:4

for V being RealLinearSpace
for v being VECTOR of V
for A, B, Aff being Subset of V st Aff is Affine & (conv A) /\ (conv B) c= Aff & conv (A \ {v}) c= Aff & not v in Aff holds
(conv (A \ {v})) /\ (conv B) = (conv A) /\ (conv B)