reserve A for non empty set,
  a,b,x,y,z,t for Element of A,
  f,g,h for Permutation of A;
reserve R for Relation of [:A,A:];
reserve AS for non empty AffinStruct;
reserve a,b,x,y for Element of AS;
reserve CS for CongrSpace;
reserve OAS for OAffinSpace;
reserve a,b,c,d,p,q,r,x,y,z,t,u for Element of OAS;
reserve f,g for Permutation of the carrier of OAS;

theorem
  for f being Permutation of the carrier of OAS st f is
  positive_dilatation holds f" is positive_dilatation
proof
  let f be Permutation of the carrier of OAS;
  assume f is positive_dilatation;
  then
A1: f is_DIL_of OAS;
  OAS is CongrSpace by Th26;
  then f" is_DIL_of OAS by A1,Th24;
  hence thesis;
end;
