proposition: Lemma tan_increasing_1 : forall x y:R, - (PI / 4) <= x -> x <= PI / 4 -> - (PI / 4) <= y -> y <= PI / 4 -> x < y -> tan x < tan y.
proof: Proof. intros; apply Rminus_lt; generalize PI4_RLT_PI2; intro H4; generalize (Ropp_lt_gt_contravar (PI / 4) (PI / 2) H4); intro H5; change (- (PI / 2) < - (PI / 4)) in H5; generalize (cos_gt_0 x (Rlt_le_trans (- (PI / 2)) (- (PI / 4)) x H5 H) (Rle_lt_trans x (PI / 4) (PI / 2) H0 H4)); intro HP1; generalize (cos_gt_0 y (Rlt_le_trans (- (PI / 2)) (- (PI / 4)) y H5 H1) (Rle_lt_trans y (PI / 4) (PI / 2) H2 H4)); intro HP2; generalize (not_eq_sym (Rlt_not_eq 0 (cos x) (cos_gt_0 x (Rlt_le_trans (- (PI / 2)) (- (PI / 4)) x H5 H) (Rle_lt_trans x (PI / 4) (PI / 2) H0 H4)))); intro H6; generalize (not_eq_sym (Rlt_not_eq 0 (cos y) (cos_gt_0 y (Rlt_le_trans (- (PI / 2)) (- (PI / 4)) y H5 H1) (Rle_lt_trans y (PI / 4) (PI / 2) H2 H4)))); intro H7; rewrite (tan_diff x y H6 H7); generalize (Rinv_0_lt_compat (cos x) HP1); intro H10; generalize (Rinv_0_lt_compat (cos y) HP2); intro H11; generalize (Rmult_lt_0_compat (/ cos x) (/ cos y) H10 H11); replace (/ cos x * / cos y) with (/ (cos x * cos y)). - clear H10 H11; intro H8; generalize (Ropp_le_ge_contravar y (PI / 4) H2); intro H11; generalize (Rge_le (- y) (- (PI / 4)) H11); clear H11; intro H11; generalize (Rplus_le_compat (- (PI / 4)) x (- (PI / 4)) (- y) H H11). replace (- (PI / 4) + - (PI / 4)) with (- (PI / 2)) by field. clear H11; intro H9; generalize (Rlt_minus x y H3); clear H3; intro H3; clear H H0 H1 H2 H4 H5 HP1 HP2; generalize PI2_Rlt_PI; intro H1; generalize (Ropp_lt_gt_contravar (PI / 2) PI H1); clear H1; intro H1; generalize (sin_lt_0_var (x - y) (Rlt_le_trans (- PI) (- (PI / 2)) (x - y) H1 H9) H3); intro H2; generalize (Rmult_lt_gt_compat_neg_l (sin (x - y)) 0 (/ (cos x * cos y)) H2 H8); rewrite Rmult_0_r; intro H4; assumption. - apply Rinv_mult. 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