theorem Th18:
  for V being ComplexLinearSpace, L being C_Linear_Combination of
V, v1, v2 being VECTOR of V holds Carrier L = {v1,v2} & v1 <> v2 implies Sum L
  = L.v1 * v1 + L.v2 * v2
proof
  let V be ComplexLinearSpace;
  let L be C_Linear_Combination of V;
  let v1, v2 be VECTOR of V;
  assume that
A1: Carrier L = {v1,v2} and
A2: v1 <> v2;
  L is C_Linear_Combination of {v1,v2} by A1,Def4;
  hence thesis by A2,Th15;
end;
