reserve x for object, X,Y for set;
reserve C for non empty set;
reserve c for Element of C;
reserve f,f1,f2,f3,g,g1 for complex-valued Function;
reserve r,p for Complex;
reserve r,r1,r2,p for Real;
reserve f,f1,f2 for PartFunc of C,REAL;
reserve f for real-valued Function;
reserve f1,f2 for real-valued Function;
reserve f,f1,f2 for PartFunc of C,REAL;

theorem Th89:
  f|Y is constant implies (p(#)f)|Y is constant
proof
  (p(#)f)|Y = p(#)(f|Y) by Th49;
  hence thesis;
end;
