reserve f,g,h for Function,
  A for set;
reserve F for Function,
  B,x,y,y1,y2,z for set;
reserve x,z for object;

theorem
  F[:](f,x)*id A = F[:](f|A,x)
proof
  thus F[:](f,x)*id A = F[:](f*id A, x) by Th29
    .= F[:](f|A, x) by RELAT_1:65;
end;
