Consider the TRS R consisting of the rewrite rules

1: f(a) -> f(b)
2: g(b) -> g(a)
3: f(x) -> g(x)

There are 3 dependency pairs:

4: F(a) -> F(b)
5: G(b) -> G(a)
6: F(x) -> G(x)

The approximated dependency graph contains no SCCs
and hence the TRS is trivially terminating.