YES
TRS:
 {f(a()) -> f(b()),
  g(b()) -> g(a())}
 DP:
  Strict:
   {f#(a()) -> f#(b()),
    g#(b()) -> g#(a())}
  Weak:
  {f(a()) -> f(b()),
   g(b()) -> g(a())}
  EDG:
   {}
   SCCS:
    
    Qed