let R be Ring; :: thesis: for V being RightMod of R
for S, T being finite Subset of V holds Sum (T /\ S) = ((Sum T) + (Sum S)) - (Sum (T \/ S))
let V be RightMod of R; :: thesis: for S, T being finite Subset of V holds Sum (T /\ S) = ((Sum T) + (Sum S)) - (Sum (T \/ S))
let S, T be finite Subset of V; :: thesis: Sum (T /\ S) = ((Sum T) + (Sum S)) - (Sum (T \/ S))
Sum (T \/ S) = ((Sum T) + (Sum S)) - (Sum (T /\ S)) by Th10;
then (Sum T) + (Sum S) = (Sum (T /\ S)) + (Sum (T \/ S)) by RLSUB_2:61;
hence Sum (T /\ S) = ((Sum T) + (Sum S)) - (Sum (T \/ S)) by RLSUB_2:61; :: thesis: verum