End Zdiv_Rdiv.
Section pow.
Variable r : radix.

Theorem radix_pos : (0 < Z2R r)%R.
Definition bpow e :=
match e with
| Zpos p => Z2R (Zpower_pos r p)
| Zneg p => Rinv (Z2R (Zpower_pos r p))
| Z0 => 1%R
end.