proposition: Lemma sin_2PI : sin (2 * PI) = 0.
proof: Proof. rewrite sin_2a; rewrite sin_PI; ring. Qed.
imports: Rbase Rfunctions SeqSeries Rtrigo_fun Rtrigo_def Rtrigo_alt Cos_rel Cos_plus ZArith_base Zcomplements Lia Lra Ranalysis1 Rsqrt_def PSeries_reg