reserve I for set,
  x,x1,x2,y,z for set,
  A for non empty set;
reserve C,D for Category;
reserve a,b,c,d for Object of C;
reserve f,g,h,i,j,k,p1,p2,q1,q2,i1,i2,j1,j2 for Morphism of C;
reserve f for Morphism of a,b,
        g for Morphism of b,a;
reserve g for Morphism of b,c;
reserve f,g for Morphism of C;

theorem Th66:
  for F being Injections_family of b,I st dom f = b holds f*F is
  Injections_family of cod f,I
proof
  let F be Injections_family of b,I;
  assume dom f = b;
  then cods F = I--> dom f by Def16;
  hence cods(f*F) = I --> cod f by Th17;
end;
