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;

theorem Th2:
  for a being Element of A st x in I holds (I --> a)/.x = a
proof
  let a be Element of A;
  assume
A1: x in I;
  hence a = (I --> a).x by FUNCOP_1:7
    .= (I --> a)/.x by A1,FUNCT_2:def 13;
end;
