chordthmlem - Metamath Proof Explorer

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Theorem chordthmlem 27167

Description: If 𝑀 is the midpoint of AB and AQ = BQ, then QMB is a right angle. The proof uses ssscongptld 27157 to observe that, since AMQ and BMQ have equal sides, the angles QMB and QMA must be equal. Since they are supplementary, both must be right angles. (Contributed by David Moews, 28-Feb-2017.)

**Hypotheses**
Ref	Expression
chordthmlem.angdef	⊢ 𝐹 = (𝑥 ∈ (ℂ ∖ {0}), 𝑦 ∈ (ℂ ∖ {0}) ↦ (ℑ‘(log‘(𝑦 / 𝑥))))
chordthmlem.A	⊢ (𝜑 → 𝐴 ∈ ℂ)
chordthmlem.B	⊢ (𝜑 → 𝐵 ∈ ℂ)
chordthmlem.Q	⊢ (𝜑 → 𝑄 ∈ ℂ)
chordthmlem.M	⊢ (𝜑 → 𝑀 = ((𝐴 + 𝐵) / 2))
chordthmlem.ABequidistQ	⊢ (𝜑 → (abs‘(𝐴 − 𝑄)) = (abs‘(𝐵 − 𝑄)))
chordthmlem.AneB	⊢ (𝜑 → 𝐴 ≠ 𝐵)
chordthmlem.QneM	⊢ (𝜑 → 𝑄 ≠ 𝑀)

**Assertion**
Ref	Expression
chordthmlem	⊢ (𝜑 → ((𝑄 − 𝑀)𝐹(𝐵 − 𝑀)) ∈ {(π / 2), -(π / 2)})

Distinct variable groups: 𝑥,𝑦,𝐴 𝑥,𝐵,𝑦 𝑥,𝑀,𝑦 𝑥,𝑄,𝑦 Allowed substitution hints: 𝜑(𝑥, 𝑦) 𝐹(𝑥, 𝑦)

**Proof of Theorem chordthmlem**
Step	Hyp	Ref	Expression
1		negpitopissre 26875	. . . . . 6 ⊢ ( -π(,]π) ⊆ ℝ
2		chordthmlem.angdef	. . . . . . 7 ⊢ 𝐹 = (𝑥 ∈ (ℂ ∖ {0}), 𝑦 ∈ (ℂ ∖ {0}) ↦ (ℑ‘(log‘(𝑦 / 𝑥))))
3		chordthmlem.Q	. . . . . . . 8 ⊢ (𝜑 → 𝑄 ∈ ℂ)
4		chordthmlem.M	. . . . . . . . 9 ⊢ (𝜑 → 𝑀 = ((𝐴 + 𝐵) / 2))
5		chordthmlem.A	. . . . . . . . . . 11 ⊢ (𝜑 → 𝐴 ∈ ℂ)
6		chordthmlem.B	. . . . . . . . . . 11 ⊢ (𝜑 → 𝐵 ∈ ℂ)
7	5, 6	addcld 11333	. . . . . . . . . 10 ⊢ (𝜑 → (𝐴 + 𝐵) ∈ ℂ)
8	7	halfcld 12596	. . . . . . . . 9 ⊢ (𝜑 → ((𝐴 + 𝐵) / 2) ∈ ℂ)
9	4, 8	eqeltrd 2860	. . . . . . . 8 ⊢ (𝜑 → 𝑀 ∈ ℂ)
10	3, 9	subcld 11674	. . . . . . 7 ⊢ (𝜑 → (𝑄 − 𝑀) ∈ ℂ)
11		chordthmlem.QneM	. . . . . . . 8 ⊢ (𝜑 → 𝑄 ≠ 𝑀)
12	3, 9, 11	subne0d 11684	. . . . . . 7 ⊢ (𝜑 → (𝑄 − 𝑀) ≠ 0)
13	6, 9	subcld 11674	. . . . . . 7 ⊢ (𝜑 → (𝐵 − 𝑀) ∈ ℂ)
14	4	oveq1d 7437	. . . . . . . . . . . . . 14 ⊢ (𝜑 → (𝑀 · 2) = (((𝐴 + 𝐵) / 2) · 2))
15	9	times2d 12595	. . . . . . . . . . . . . 14 ⊢ (𝜑 → (𝑀 · 2) = (𝑀 + 𝑀))
16		2cnd 12426	. . . . . . . . . . . . . . 15 ⊢ (𝜑 → 2 ∈ ℂ)
17		2ne0 12454	. . . . . . . . . . . . . . . 16 ⊢ 2 ≠ 0
18	17	a1i 11	. . . . . . . . . . . . . . 15 ⊢ (𝜑 → 2 ≠ 0)
19	7, 16, 18	divcan1d 12099	. . . . . . . . . . . . . 14 ⊢ (𝜑 → (((𝐴 + 𝐵) / 2) · 2) = (𝐴 + 𝐵))
20	14, 15, 19	3eqtr3d 2803	. . . . . . . . . . . . 13 ⊢ (𝜑 → (𝑀 + 𝑀) = (𝐴 + 𝐵))
21		chordthmlem.AneB	. . . . . . . . . . . . . 14 ⊢ (𝜑 → 𝐴 ≠ 𝐵)
22	5, 6, 6, 21	addneintr2d 11523	. . . . . . . . . . . . 13 ⊢ (𝜑 → (𝐴 + 𝐵) ≠ (𝐵 + 𝐵))
23	20, 22	eqnetrd 3022	. . . . . . . . . . . 12 ⊢ (𝜑 → (𝑀 + 𝑀) ≠ (𝐵 + 𝐵))
24	23	neneqd 2960	. . . . . . . . . . 11 ⊢ (𝜑 → ¬ (𝑀 + 𝑀) = (𝐵 + 𝐵))
25		oveq12 7431	. . . . . . . . . . . 12 ⊢ ((𝑀 = 𝐵 ∧ 𝑀 = 𝐵) → (𝑀 + 𝑀) = (𝐵 + 𝐵))
26	25	anidms 577	. . . . . . . . . . 11 ⊢ (𝑀 = 𝐵 → (𝑀 + 𝑀) = (𝐵 + 𝐵))
27	24, 26	nsyl 141	. . . . . . . . . 10 ⊢ (𝜑 → ¬ 𝑀 = 𝐵)
28	27	neqned 2962	. . . . . . . . 9 ⊢ (𝜑 → 𝑀 ≠ 𝐵)
29	28	necomd 3010	. . . . . . . 8 ⊢ (𝜑 → 𝐵 ≠ 𝑀)
30	6, 9, 29	subne0d 11684	. . . . . . 7 ⊢ (𝜑 → (𝐵 − 𝑀) ≠ 0)
31	2, 10, 12, 13, 30	angcld 27140	. . . . . 6 ⊢ (𝜑 → ((𝑄 − 𝑀)𝐹(𝐵 − 𝑀)) ∈ ( -π(,]π))
32	1, 31	sselid 3907	. . . . 5 ⊢ (𝜑 → ((𝑄 − 𝑀)𝐹(𝐵 − 𝑀)) ∈ ℝ)
33	32	recnd 11342	. . . 4 ⊢ (𝜑 → ((𝑄 − 𝑀)𝐹(𝐵 − 𝑀)) ∈ ℂ)
34	33	coscld 16306	. . 3 ⊢ (𝜑 → (cos‘((𝑄 − 𝑀)𝐹(𝐵 − 𝑀))) ∈ ℂ)
35	6, 9	negsubdi2d 11690	. . . . . . 7 ⊢ (𝜑 → -(𝐵 − 𝑀) = (𝑀 − 𝐵))
36	9, 9, 5, 6	addsubeq4d 11725	. . . . . . . 8 ⊢ (𝜑 → ((𝑀 + 𝑀) = (𝐴 + 𝐵) ↔ (𝐴 − 𝑀) = (𝑀 − 𝐵)))
37	20, 36	mpbid 235	. . . . . . 7 ⊢ (𝜑 → (𝐴 − 𝑀) = (𝑀 − 𝐵))
38	35, 37	eqtr4d 2798	. . . . . 6 ⊢ (𝜑 → -(𝐵 − 𝑀) = (𝐴 − 𝑀))
39	38	oveq2d 7438	. . . . 5 ⊢ (𝜑 → ((𝑄 − 𝑀)𝐹 -(𝐵 − 𝑀)) = ((𝑄 − 𝑀)𝐹(𝐴 − 𝑀)))
40	39	fveq2d 6892	. . . 4 ⊢ (𝜑 → (cos‘((𝑄 − 𝑀)𝐹 -(𝐵 − 𝑀))) = (cos‘((𝑄 − 𝑀)𝐹(𝐴 − 𝑀))))
41	2, 10, 12, 13, 30	cosangneg2d 27142	. . . 4 ⊢ (𝜑 → (cos‘((𝑄 − 𝑀)𝐹 -(𝐵 − 𝑀))) = -(cos‘((𝑄 − 𝑀)𝐹(𝐵 − 𝑀))))
42	5, 5, 6, 21	addneintrd 11522	. . . . . . . . . 10 ⊢ (𝜑 → (𝐴 + 𝐴) ≠ (𝐴 + 𝐵))
43	42, 20	neeqtrrd 3029	. . . . . . . . 9 ⊢ (𝜑 → (𝐴 + 𝐴) ≠ (𝑀 + 𝑀))
44	43	necomd 3010	. . . . . . . 8 ⊢ (𝜑 → (𝑀 + 𝑀) ≠ (𝐴 + 𝐴))
45	44	neneqd 2960	. . . . . . 7 ⊢ (𝜑 → ¬ (𝑀 + 𝑀) = (𝐴 + 𝐴))
46		oveq12 7431	. . . . . . . 8 ⊢ ((𝑀 = 𝐴 ∧ 𝑀 = 𝐴) → (𝑀 + 𝑀) = (𝐴 + 𝐴))
47	46	anidms 577	. . . . . . 7 ⊢ (𝑀 = 𝐴 → (𝑀 + 𝑀) = (𝐴 + 𝐴))
48	45, 47	nsyl 141	. . . . . 6 ⊢ (𝜑 → ¬ 𝑀 = 𝐴)
49	48	neqned 2962	. . . . 5 ⊢ (𝜑 → 𝑀 ≠ 𝐴)
50		eqidd 2761	. . . . 5 ⊢ (𝜑 → (abs‘(𝑄 − 𝑀)) = (abs‘(𝑄 − 𝑀)))
51	5, 9	subcld 11674	. . . . . . 7 ⊢ (𝜑 → (𝐴 − 𝑀) ∈ ℂ)
52	51	absnegd 15626	. . . . . 6 ⊢ (𝜑 → (abs‘ -(𝐴 − 𝑀)) = (abs‘(𝐴 − 𝑀)))
53	5, 9	negsubdi2d 11690	. . . . . . 7 ⊢ (𝜑 → -(𝐴 − 𝑀) = (𝑀 − 𝐴))
54	53	fveq2d 6892	. . . . . 6 ⊢ (𝜑 → (abs‘ -(𝐴 − 𝑀)) = (abs‘(𝑀 − 𝐴)))
55	37	fveq2d 6892	. . . . . 6 ⊢ (𝜑 → (abs‘(𝐴 − 𝑀)) = (abs‘(𝑀 − 𝐵)))
56	52, 54, 55	3eqtr3d 2803	. . . . 5 ⊢ (𝜑 → (abs‘(𝑀 − 𝐴)) = (abs‘(𝑀 − 𝐵)))
57		chordthmlem.ABequidistQ	. . . . 5 ⊢ (𝜑 → (abs‘(𝐴 − 𝑄)) = (abs‘(𝐵 − 𝑄)))
58	2, 3, 9, 5, 3, 9, 6, 11, 49, 11, 28, 50, 56, 57	ssscongptld 27157	. . . 4 ⊢ (𝜑 → (cos‘((𝑄 − 𝑀)𝐹(𝐴 − 𝑀))) = (cos‘((𝑄 − 𝑀)𝐹(𝐵 − 𝑀))))
59	40, 41, 58	3eqtr3rd 2804	. . 3 ⊢ (𝜑 → (cos‘((𝑄 − 𝑀)𝐹(𝐵 − 𝑀))) = -(cos‘((𝑄 − 𝑀)𝐹(𝐵 − 𝑀))))
60	34, 59	eqnegad 12044	. 2 ⊢ (𝜑 → (cos‘((𝑄 − 𝑀)𝐹(𝐵 − 𝑀))) = 0)
61		coseq0negpitopi 26839	. . 3 ⊢ (((𝑄 − 𝑀)𝐹(𝐵 − 𝑀)) ∈ ( -π(,]π) → ((cos‘((𝑄 − 𝑀)𝐹(𝐵 − 𝑀))) = 0 ↔ ((𝑄 − 𝑀)𝐹(𝐵 − 𝑀)) ∈ {(π / 2), -(π / 2)}))
62	31, 61	syl 18	. 2 ⊢ (𝜑 → ((cos‘((𝑄 − 𝑀)𝐹(𝐵 − 𝑀))) = 0 ↔ ((𝑄 − 𝑀)𝐹(𝐵 − 𝑀)) ∈ {(π / 2), -(π / 2)}))
63	60, 62	mpbid 235	1 ⊢ (𝜑 → ((𝑄 − 𝑀)𝐹(𝐵 − 𝑀)) ∈ {(π / 2), -(π / 2)})

Colors of variables: wff setvar class

This proof depends on syntax axioms: → wi 4 ↔ wb 209 = wceq 1569 ∈ wcel 2144 ≠ wne 2955 ∖ cdif 4044 {csn 4584 {cpr 4586 ‘cfv 6541 (class class class)co 7422 ∈ cmpo 7424 ℂcc 11203 ℝcr 11204 0cc0 11205 + caddc 11208 · cmul 11210 − cmin 11546 -cneg 11547 / cdiv 11978 2c2 12402 (,]cioc 13482 ℑcim 15272 abscabs 15408 cosccos 16237 πcpi 16239 logclog 26889

This proof depends on axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1827 ax-4 1841 ax-5 1942 ax-6 1999 ax-7 2040 ax-8 2146 ax-9 2154 ax-10 2177 ax-11 2193 ax-12 2212 ax-ext 2732 ax-rep 5231 ax-sep 5248 ax-nul 5259 ax-pow 5326 ax-pr 5390 ax-un 7753 ax-inf2 9647 ax-cnex 11261 ax-resscn 11262 ax-1cn 11263 ax-icn 11264 ax-addcl 11265 ax-addrcl 11266 ax-mulcl 11267 ax-mulrcl 11268 ax-mulcom 11269 ax-addass 11270 ax-mulass 11271 ax-distr 11272 ax-i2m1 11273 ax-1ne0 11274 ax-1rid 11275 ax-rnegex 11276 ax-rrecex 11277 ax-cnre 11278 ax-pre-lttri 11279 ax-pre-lttrn 11280 ax-pre-ltadd 11281 ax-pre-mulgt0 11282 ax-pre-sup 11283 ax-addf 11284

This proof depends on definitions: df-bi 210 df-an 402 df-or 862 df-3or 1104 df-3an 1105 df-tru 1572 df-fal 1582 df-ex 1812 df-nf 1816 df-sb 2099 df-mo 2564 df-eu 2594 df-clab 2739 df-cleq 2752 df-clel 2835 df-nfc 2909 df-ne 2956 df-nel 3062 df-ral 3077 df-rex 3087 df-rmo 3365 df-reu 3366 df-rab 3413 df-v 3452 df-sbc 3739 df-csb 3848 df-ss 3897 df-pss 4013 df-dif 4046 df-in 4090 df-un 4150 df-nul 4278 df-if 4482 df-pw 4558 df-sn 4585 df-pr 4587 df-tp 4589 df-op 4835 df-uni 4867 df-int 4907 df-iun 4952 df-iin 4953 df-br 5103 df-opab 5167 df-mpt 5186 df-tr 5212 df-id 5545 df-eprel 5550 df-po 5558 df-so 5559 df-fr 5603 df-se 5604 df-we 5605 df-xp 5656 df-rel 5657 df-cnv 5658 df-co 5659 df-dm 5660 df-rn 5661 df-res 5662 df-ima 5663 df-pred 6306 df-ord 6367 df-on 6368 df-lim 6369 df-suc 6370 df-iota 6496 df-fun 6543 df-fn 6544 df-f 6545 df-f1 6546 df-fo 6547 df-f1o 6548 df-fv 6549 df-isom 6550 df-riota 7379 df-ov 7425 df-oprab 7426 df-mpo 7427 df-of 7695 df-om 7880 df-1st 8003 df-2nd 8004 df-supp 8182 df-frecs 8304 df-wrecs 8335 df-recs 8384 df-rdg 8423 df-1o 8481 df-2o 8482 df-er 8722 df-map 8854 df-pm 8855 df-ixp 8931 df-en 8979 df-dom 8980 df-sdom 8981 df-fin 8982 df-fsupp 9359 df-fi 9408 df-sup 9439 df-inf 9440 df-oi 9509 df-card 10025 df-pnf 11350 df-mnf 11351 df-xr 11352 df-ltxr 11353 df-le 11354 df-sub 11548 df-neg 11549 df-div 11979 df-nn 12341 df-2 12410 df-3 12411 df-4 12412 df-5 12413 df-6 12414 df-7 12415 df-8 12416 df-9 12417 df-n0 12612 df-z 12699 df-dec 12820 df-uz 12971 df-q 13081 df-rp 13126 df-xneg 13246 df-xadd 13247 df-xmul 13248 df-ioo 13485 df-ioc 13486 df-ico 13487 df-icc 13488 df-fz 13645 df-fzo 13794 df-fl 13937 df-mod 14015 df-seq 14150 df-exp 14210 df-fac 14423 df-bc 14452 df-hash 14480 df-shft 15227 df-cj 15273 df-re 15274 df-im 15275 df-sqrt 15409 df-abs 15410 df-limsup 15645 df-clim 15662 df-rlim 15663 df-sum 15861 df-ef 16240 df-sin 16242 df-cos 16243 df-pi 16245 df-struct 17332 df-sets 17349 df-slot 17367 df-ndx 17379 df-base 17395 df-ress 17416 df-plusg 17448 df-mulr 17449 df-starv 17450 df-sca 17451 df-vsca 17452 df-ip 17453 df-tset 17454 df-ple 17455 df-ds 17457 df-unif 17458 df-hom 17459 df-cco 17460 df-rest 17600 df-topn 17601 df-0g 17619 df-gsum 17620 df-topgen 17621 df-pt 17622 df-prds 17625 df-xrs 17681 df-qtop 17686 df-imas 17687 df-xps 17689 df-mre 17763 df-mrc 17764 df-acs 17766 df-mgm 18823 df-sgrp 18915 df-mnd 18931 df-submnd 18986 df-mulg 19285 df-cntz 19538 df-cmn 20003 df-psmet 21677 df-xmet 21678 df-met 21679 df-bl 21680 df-mopn 21681 df-fbas 21682 df-fg 21683 df-cnfld 21686 df-top 23219 df-topon 23236 df-topsp 23258 df-bases 23271 df-cld 23344 df-ntr 23345 df-cls 23346 df-nei 23423 df-lp 23461 df-perf 23462 df-cn 23552 df-cnp 23553 df-haus 23640 df-tx 23888 df-hmeo 24081 df-fil 24172 df-fm 24264 df-flim 24265 df-flf 24266 df-xms 24646 df-ms 24647 df-tms 24648 df-cncf 25206 df-limc 26193 df-dv 26194 df-log 26891

This theorem is used by: chordthmlem2 27168

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