let V be non empty right_complementable Abelian add-associative right_zeroed addLoopStr ; :: thesis: for v1, v2 being Element of V st v1 <> v2 holds
Sum {v1,v2} = v1 + v2
let v1, v2 be Element of V; :: thesis: ( v1 <> v2 implies Sum {v1,v2} = v1 + v2 )
assume v1 <> v2 ; :: thesis: Sum {v1,v2} = v1 + v2
then ( rng <*v1,v2*> = {v1,v2} & <*v1,v2*> is one-to-one & Sum <*v1,v2*> = v1 + v2 ) by FINSEQ_2:147, FINSEQ_3:103, RLVECT_1:62;
hence Sum {v1,v2} = v1 + v2 by Def4; :: thesis: verum