proposition: Lemma tan_gt_0 : forall x:R, 0 < x -> x < PI / 2 -> 0 < tan x.
proof: Proof. intros x H1 H2; unfold tan in |- *; generalize _PI2_RLT_0; generalize (Rlt_trans 0 x (PI / 2) H1 H2); intros; generalize (Rlt_trans (- (PI / 2)) 0 x H0 H1); intro H5; generalize (Rlt_trans x (PI / 2) PI H2 PI2_Rlt_PI); intro H7; unfold Rdiv in |- *; apply Rmult_lt_0_compat. - apply sin_gt_0; assumption. - apply Rinv_0_lt_compat; apply cos_gt_0; assumption. 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