proposition: Lemma BRdiv_diag_rw x y: realp x -> realp y -> x /r y = \1r -> x = y.
proof: Proof. move => xr yr h. case: (equal_or_not y \0r) => h'. by move: h; rewrite h' (BRdiv_x0) => hh; case: BR_one_nz. by move:(f_equal (BRprod y) h); rewrite (BRprod_div yr xr h') BRprod_1r. Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)