cosq14gt0 - Intuitionistic Logic Explorer

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Theorem cosq14gt0 13547

Description: The cosine of a number strictly between -π / 2 and π / 2 is positive. (Contributed by Mario Carneiro, 25-Feb-2015.)

**Assertion**
Ref	Expression
cosq14gt0	⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → 0 < (cos‘𝐴))

**Proof of Theorem cosq14gt0**
Step	Hyp	Ref	Expression
1		halfpire 13507	. . . . 5 ⊢ (π / 2) ∈ ℝ
2		elioore 9869	. . . . 5 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → 𝐴 ∈ ℝ)
3		resubcl 8183	. . . . 5 ⊢ (((π / 2) ∈ ℝ ∧ 𝐴 ∈ ℝ) → ((π / 2) − 𝐴) ∈ ℝ)
4	1, 2, 3	sylancr 412	. . . 4 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → ((π / 2) − 𝐴) ∈ ℝ)
5		neghalfpirx 13509	. . . . . . 7 ⊢ -(π / 2) ∈ ℝ^*
6	1	rexri 7977	. . . . . . 7 ⊢ (π / 2) ∈ ℝ^*
7		elioo2 9878	. . . . . . 7 ⊢ ((-(π / 2) ∈ ℝ^* ∧ (π / 2) ∈ ℝ^*) → (𝐴 ∈ (-(π / 2)(,)(π / 2)) ↔ (𝐴 ∈ ℝ ∧ -(π / 2) < 𝐴 ∧ 𝐴 < (π / 2))))
8	5, 6, 7	mp2an 424	. . . . . 6 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) ↔ (𝐴 ∈ ℝ ∧ -(π / 2) < 𝐴 ∧ 𝐴 < (π / 2)))
9	8	simp3bi 1009	. . . . 5 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → 𝐴 < (π / 2))
10		posdif 8374	. . . . . 6 ⊢ ((𝐴 ∈ ℝ ∧ (π / 2) ∈ ℝ) → (𝐴 < (π / 2) ↔ 0 < ((π / 2) − 𝐴)))
11	2, 1, 10	sylancl 411	. . . . 5 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → (𝐴 < (π / 2) ↔ 0 < ((π / 2) − 𝐴)))
12	9, 11	mpbid 146	. . . 4 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → 0 < ((π / 2) − 𝐴))
13		picn 13502	. . . . . . . 8 ⊢ π ∈ ℂ
14		halfcl 9104	. . . . . . . 8 ⊢ (π ∈ ℂ → (π / 2) ∈ ℂ)
15	13, 14	ax-mp 5	. . . . . . 7 ⊢ (π / 2) ∈ ℂ
16	15	negcli 8187	. . . . . . 7 ⊢ -(π / 2) ∈ ℂ
17	13, 15	negsubi 8197	. . . . . . . 8 ⊢ (π + -(π / 2)) = (π − (π / 2))
18		pidiv2halves 13510	. . . . . . . . 9 ⊢ ((π / 2) + (π / 2)) = π
19	13, 15, 15, 18	subaddrii 8208	. . . . . . . 8 ⊢ (π − (π / 2)) = (π / 2)
20	17, 19	eqtri 2191	. . . . . . 7 ⊢ (π + -(π / 2)) = (π / 2)
21	15, 13, 16, 20	subaddrii 8208	. . . . . 6 ⊢ ((π / 2) − π) = -(π / 2)
22	8	simp2bi 1008	. . . . . 6 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → -(π / 2) < 𝐴)
23	21, 22	eqbrtrid 4024	. . . . 5 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → ((π / 2) − π) < 𝐴)
24		pire 13501	. . . . . . 7 ⊢ π ∈ ℝ
25		ltsub23 8361	. . . . . . 7 ⊢ (((π / 2) ∈ ℝ ∧ 𝐴 ∈ ℝ ∧ π ∈ ℝ) → (((π / 2) − 𝐴) < π ↔ ((π / 2) − π) < 𝐴))
26	1, 24, 25	mp3an13 1323	. . . . . 6 ⊢ (𝐴 ∈ ℝ → (((π / 2) − 𝐴) < π ↔ ((π / 2) − π) < 𝐴))
27	2, 26	syl 14	. . . . 5 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → (((π / 2) − 𝐴) < π ↔ ((π / 2) − π) < 𝐴))
28	23, 27	mpbird 166	. . . 4 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → ((π / 2) − 𝐴) < π)
29		0xr 7966	. . . . 5 ⊢ 0 ∈ ℝ^*
30	24	rexri 7977	. . . . 5 ⊢ π ∈ ℝ^*
31		elioo2 9878	. . . . 5 ⊢ ((0 ∈ ℝ^* ∧ π ∈ ℝ^*) → (((π / 2) − 𝐴) ∈ (0(,)π) ↔ (((π / 2) − 𝐴) ∈ ℝ ∧ 0 < ((π / 2) − 𝐴) ∧ ((π / 2) − 𝐴) < π)))
32	29, 30, 31	mp2an 424	. . . 4 ⊢ (((π / 2) − 𝐴) ∈ (0(,)π) ↔ (((π / 2) − 𝐴) ∈ ℝ ∧ 0 < ((π / 2) − 𝐴) ∧ ((π / 2) − 𝐴) < π))
33	4, 12, 28, 32	syl3anbrc 1176	. . 3 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → ((π / 2) − 𝐴) ∈ (0(,)π))
34		sinq12gt0 13545	. . 3 ⊢ (((π / 2) − 𝐴) ∈ (0(,)π) → 0 < (sin‘((π / 2) − 𝐴)))
35	33, 34	syl 14	. 2 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → 0 < (sin‘((π / 2) − 𝐴)))
36	2	recnd 7948	. . 3 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → 𝐴 ∈ ℂ)
37		sinhalfpim 13536	. . 3 ⊢ (𝐴 ∈ ℂ → (sin‘((π / 2) − 𝐴)) = (cos‘𝐴))
38	36, 37	syl 14	. 2 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → (sin‘((π / 2) − 𝐴)) = (cos‘𝐴))
39	35, 38	breqtrd 4015	1 ⊢ (𝐴 ∈ (-(π / 2)(,)(π / 2)) → 0 < (cos‘𝐴))

Colors of variables: wff set class

Syntax hints: → wi 4 ↔ wb 104 ∧ w3a 973 = wceq 1348 ∈ wcel 2141 class class class wbr 3989 ‘cfv 5198 (class class class)co 5853 ℂcc 7772 ℝcr 7773 0cc0 7774 + caddc 7777 ℝ^*cxr 7953 < clt 7954 − cmin 8090 -cneg 8091 / cdiv 8589 2c2 8929 (,)cioo 9845 sincsin 11607 cosccos 11608 πcpi 11610

This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-ia1 105 ax-ia2 106 ax-ia3 107 ax-in1 609 ax-in2 610 ax-io 704 ax-5 1440 ax-7 1441 ax-gen 1442 ax-ie1 1486 ax-ie2 1487 ax-8 1497 ax-10 1498 ax-11 1499 ax-i12 1500 ax-bndl 1502 ax-4 1503 ax-17 1519 ax-i9 1523 ax-ial 1527 ax-i5r 1528 ax-13 2143 ax-14 2144 ax-ext 2152 ax-coll 4104 ax-sep 4107 ax-nul 4115 ax-pow 4160 ax-pr 4194 ax-un 4418 ax-setind 4521 ax-iinf 4572 ax-cnex 7865 ax-resscn 7866 ax-1cn 7867 ax-1re 7868 ax-icn 7869 ax-addcl 7870 ax-addrcl 7871 ax-mulcl 7872 ax-mulrcl 7873 ax-addcom 7874 ax-mulcom 7875 ax-addass 7876 ax-mulass 7877 ax-distr 7878 ax-i2m1 7879 ax-0lt1 7880 ax-1rid 7881 ax-0id 7882 ax-rnegex 7883 ax-precex 7884 ax-cnre 7885 ax-pre-ltirr 7886 ax-pre-ltwlin 7887 ax-pre-lttrn 7888 ax-pre-apti 7889 ax-pre-ltadd 7890 ax-pre-mulgt0 7891 ax-pre-mulext 7892 ax-arch 7893 ax-caucvg 7894 ax-pre-suploc 7895 ax-addf 7896 ax-mulf 7897

This theorem depends on definitions: df-bi 116 df-stab 826 df-dc 830 df-3or 974 df-3an 975 df-tru 1351 df-fal 1354 df-nf 1454 df-sb 1756 df-eu 2022 df-mo 2023 df-clab 2157 df-cleq 2163 df-clel 2166 df-nfc 2301 df-ne 2341 df-nel 2436 df-ral 2453 df-rex 2454 df-reu 2455 df-rmo 2456 df-rab 2457 df-v 2732 df-sbc 2956 df-csb 3050 df-dif 3123 df-un 3125 df-in 3127 df-ss 3134 df-nul 3415 df-if 3527 df-pw 3568 df-sn 3589 df-pr 3590 df-op 3592 df-uni 3797 df-int 3832 df-iun 3875 df-disj 3967 df-br 3990 df-opab 4051 df-mpt 4052 df-tr 4088 df-id 4278 df-po 4281 df-iso 4282 df-iord 4351 df-on 4353 df-ilim 4354 df-suc 4356 df-iom 4575 df-xp 4617 df-rel 4618 df-cnv 4619 df-co 4620 df-dm 4621 df-rn 4622 df-res 4623 df-ima 4624 df-iota 5160 df-fun 5200 df-fn 5201 df-f 5202 df-f1 5203 df-fo 5204 df-f1o 5205 df-fv 5206 df-isom 5207 df-riota 5809 df-ov 5856 df-oprab 5857 df-mpo 5858 df-of 6061 df-1st 6119 df-2nd 6120 df-recs 6284 df-irdg 6349 df-frec 6370 df-1o 6395 df-oadd 6399 df-er 6513 df-map 6628 df-pm 6629 df-en 6719 df-dom 6720 df-fin 6721 df-sup 6961 df-inf 6962 df-pnf 7956 df-mnf 7957 df-xr 7958 df-ltxr 7959 df-le 7960 df-sub 8092 df-neg 8093 df-reap 8494 df-ap 8501 df-div 8590 df-inn 8879 df-2 8937 df-3 8938 df-4 8939 df-5 8940 df-6 8941 df-7 8942 df-8 8943 df-9 8944 df-n0 9136 df-z 9213 df-uz 9488 df-q 9579 df-rp 9611 df-xneg 9729 df-xadd 9730 df-ioo 9849 df-ioc 9850 df-ico 9851 df-icc 9852 df-fz 9966 df-fzo 10099 df-seqfrec 10402 df-exp 10476 df-fac 10660 df-bc 10682 df-ihash 10710 df-shft 10779 df-cj 10806 df-re 10807 df-im 10808 df-rsqrt 10962 df-abs 10963 df-clim 11242 df-sumdc 11317 df-ef 11611 df-sin 11613 df-cos 11614 df-pi 11616 df-rest 12581 df-topgen 12600 df-psmet 12781 df-xmet 12782 df-met 12783 df-bl 12784 df-mopn 12785 df-top 12790 df-topon 12803 df-bases 12835 df-ntr 12890 df-cn 12982 df-cnp 12983 df-tx 13047 df-cncf 13352 df-limced 13419 df-dvap 13420

This theorem is referenced by: coseq0q4123 13549

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