Definition sind (x:R) : R := sin (toRad x).Definition cosd (x:R) : R := cos (toRad x).Definition tand (x:R) : R := tan (toRad x).

(* Specifications: *)
Lemma Rsqr_sin_cos_d_one : forall x:R, Rsqr (sind x) + Rsqr (cosd x) = 1.
Lemma sin_lb_ge_0 : forall a:R, 0 <= a -> a <= PI / 2 -> 0 <= sin_lb a.