theorem
  Carrier(L) = {v1,v2} & v1 <> v2 implies Sum(L) = v1 * L.v1 + v2 * L.v2
proof
  assume that
A1: Carrier(L) = {v1,v2} and
A2: v1 <> v2;
  L is Linear_Combination of {v1,v2} by A1,Def5;
  hence thesis by A2,Th33;
end;
