reserve E,F,G for RealNormSpace;
reserve f for Function of E,F;
reserve g for Function of F,G;
reserve a,b,c for Point of E;
reserve t for Real;

theorem Th3:
  a + a = 2*a
  proof
    1*a = a by RLVECT_1:def 8;
    hence a + a = (1+1)*a by RLVECT_1:def 6
    .= 2*a;
  end;
