reserve a,b for Complex;
reserve V,X,Y for ComplexLinearSpace;
reserve u,u1,u2,v,v1,v2 for VECTOR of V;
reserve z,z1,z2 for Complex;

theorem
  v + v = 0.V implies v = 0.V
proof
  assume v + v = 0.V;
  then v = - v by RLVECT_1:def 10;
  hence thesis by Th4;
end;
