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Theorem phpar 27528
Description: The parallelogram law for an inner product space. (Contributed by NM, 2-Apr-2007.) (New usage is discouraged.)
Hypotheses
Ref Expression
phpar.1 𝑋 = (BaseSet‘𝑈)
phpar.2 𝐺 = ( +𝑣𝑈)
phpar.4 𝑆 = ( ·𝑠OLD𝑈)
phpar.6 𝑁 = (normCV𝑈)
Assertion
Ref Expression
phpar ((𝑈 ∈ CPreHilOLD𝐴𝑋𝐵𝑋) → (((𝑁‘(𝐴𝐺𝐵))↑2) + ((𝑁‘(𝐴𝐺(-1𝑆𝐵)))↑2)) = (2 · (((𝑁𝐴)↑2) + ((𝑁𝐵)↑2))))

Proof of Theorem phpar
Dummy variables 𝑥 𝑦 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 phpar.2 . . . . . . 7 𝐺 = ( +𝑣𝑈)
21vafval 27307 . . . . . 6 𝐺 = (1st ‘(1st𝑈))
3 fvex 6158 . . . . . 6 (1st ‘(1st𝑈)) ∈ V
42, 3eqeltri 2694 . . . . 5 𝐺 ∈ V
5 phpar.4 . . . . . . 7 𝑆 = ( ·𝑠OLD𝑈)
65smfval 27309 . . . . . 6 𝑆 = (2nd ‘(1st𝑈))
7 fvex 6158 . . . . . 6 (2nd ‘(1st𝑈)) ∈ V
86, 7eqeltri 2694 . . . . 5 𝑆 ∈ V
9 phpar.6 . . . . . . 7 𝑁 = (normCV𝑈)
109nmcvfval 27311 . . . . . 6 𝑁 = (2nd𝑈)
11 fvex 6158 . . . . . 6 (2nd𝑈) ∈ V
1210, 11eqeltri 2694 . . . . 5 𝑁 ∈ V
134, 8, 123pm3.2i 1237 . . . 4 (𝐺 ∈ V ∧ 𝑆 ∈ V ∧ 𝑁 ∈ V)
141, 5, 9phop 27522 . . . . . 6 (𝑈 ∈ CPreHilOLD𝑈 = ⟨⟨𝐺, 𝑆⟩, 𝑁⟩)
1514eleq1d 2683 . . . . 5 (𝑈 ∈ CPreHilOLD → (𝑈 ∈ CPreHilOLD ↔ ⟨⟨𝐺, 𝑆⟩, 𝑁⟩ ∈ CPreHilOLD))
1615ibi 256 . . . 4 (𝑈 ∈ CPreHilOLD → ⟨⟨𝐺, 𝑆⟩, 𝑁⟩ ∈ CPreHilOLD)
17 phpar.1 . . . . . . 7 𝑋 = (BaseSet‘𝑈)
1817, 1bafval 27308 . . . . . 6 𝑋 = ran 𝐺
1918isphg 27521 . . . . 5 ((𝐺 ∈ V ∧ 𝑆 ∈ V ∧ 𝑁 ∈ V) → (⟨⟨𝐺, 𝑆⟩, 𝑁⟩ ∈ CPreHilOLD ↔ (⟨⟨𝐺, 𝑆⟩, 𝑁⟩ ∈ NrmCVec ∧ ∀𝑥𝑋𝑦𝑋 (((𝑁‘(𝑥𝐺𝑦))↑2) + ((𝑁‘(𝑥𝐺(-1𝑆𝑦)))↑2)) = (2 · (((𝑁𝑥)↑2) + ((𝑁𝑦)↑2))))))
2019simplbda 653 . . . 4 (((𝐺 ∈ V ∧ 𝑆 ∈ V ∧ 𝑁 ∈ V) ∧ ⟨⟨𝐺, 𝑆⟩, 𝑁⟩ ∈ CPreHilOLD) → ∀𝑥𝑋𝑦𝑋 (((𝑁‘(𝑥𝐺𝑦))↑2) + ((𝑁‘(𝑥𝐺(-1𝑆𝑦)))↑2)) = (2 · (((𝑁𝑥)↑2) + ((𝑁𝑦)↑2))))
2113, 16, 20sylancr 694 . . 3 (𝑈 ∈ CPreHilOLD → ∀𝑥𝑋𝑦𝑋 (((𝑁‘(𝑥𝐺𝑦))↑2) + ((𝑁‘(𝑥𝐺(-1𝑆𝑦)))↑2)) = (2 · (((𝑁𝑥)↑2) + ((𝑁𝑦)↑2))))
22213ad2ant1 1080 . 2 ((𝑈 ∈ CPreHilOLD𝐴𝑋𝐵𝑋) → ∀𝑥𝑋𝑦𝑋 (((𝑁‘(𝑥𝐺𝑦))↑2) + ((𝑁‘(𝑥𝐺(-1𝑆𝑦)))↑2)) = (2 · (((𝑁𝑥)↑2) + ((𝑁𝑦)↑2))))
23 oveq1 6611 . . . . . . . 8 (𝑥 = 𝐴 → (𝑥𝐺𝑦) = (𝐴𝐺𝑦))
2423fveq2d 6152 . . . . . . 7 (𝑥 = 𝐴 → (𝑁‘(𝑥𝐺𝑦)) = (𝑁‘(𝐴𝐺𝑦)))
2524oveq1d 6619 . . . . . 6 (𝑥 = 𝐴 → ((𝑁‘(𝑥𝐺𝑦))↑2) = ((𝑁‘(𝐴𝐺𝑦))↑2))
26 oveq1 6611 . . . . . . . 8 (𝑥 = 𝐴 → (𝑥𝐺(-1𝑆𝑦)) = (𝐴𝐺(-1𝑆𝑦)))
2726fveq2d 6152 . . . . . . 7 (𝑥 = 𝐴 → (𝑁‘(𝑥𝐺(-1𝑆𝑦))) = (𝑁‘(𝐴𝐺(-1𝑆𝑦))))
2827oveq1d 6619 . . . . . 6 (𝑥 = 𝐴 → ((𝑁‘(𝑥𝐺(-1𝑆𝑦)))↑2) = ((𝑁‘(𝐴𝐺(-1𝑆𝑦)))↑2))
2925, 28oveq12d 6622 . . . . 5 (𝑥 = 𝐴 → (((𝑁‘(𝑥𝐺𝑦))↑2) + ((𝑁‘(𝑥𝐺(-1𝑆𝑦)))↑2)) = (((𝑁‘(𝐴𝐺𝑦))↑2) + ((𝑁‘(𝐴𝐺(-1𝑆𝑦)))↑2)))
30 fveq2 6148 . . . . . . . 8 (𝑥 = 𝐴 → (𝑁𝑥) = (𝑁𝐴))
3130oveq1d 6619 . . . . . . 7 (𝑥 = 𝐴 → ((𝑁𝑥)↑2) = ((𝑁𝐴)↑2))
3231oveq1d 6619 . . . . . 6 (𝑥 = 𝐴 → (((𝑁𝑥)↑2) + ((𝑁𝑦)↑2)) = (((𝑁𝐴)↑2) + ((𝑁𝑦)↑2)))
3332oveq2d 6620 . . . . 5 (𝑥 = 𝐴 → (2 · (((𝑁𝑥)↑2) + ((𝑁𝑦)↑2))) = (2 · (((𝑁𝐴)↑2) + ((𝑁𝑦)↑2))))
3429, 33eqeq12d 2636 . . . 4 (𝑥 = 𝐴 → ((((𝑁‘(𝑥𝐺𝑦))↑2) + ((𝑁‘(𝑥𝐺(-1𝑆𝑦)))↑2)) = (2 · (((𝑁𝑥)↑2) + ((𝑁𝑦)↑2))) ↔ (((𝑁‘(𝐴𝐺𝑦))↑2) + ((𝑁‘(𝐴𝐺(-1𝑆𝑦)))↑2)) = (2 · (((𝑁𝐴)↑2) + ((𝑁𝑦)↑2)))))
35 oveq2 6612 . . . . . . . 8 (𝑦 = 𝐵 → (𝐴𝐺𝑦) = (𝐴𝐺𝐵))
3635fveq2d 6152 . . . . . . 7 (𝑦 = 𝐵 → (𝑁‘(𝐴𝐺𝑦)) = (𝑁‘(𝐴𝐺𝐵)))
3736oveq1d 6619 . . . . . 6 (𝑦 = 𝐵 → ((𝑁‘(𝐴𝐺𝑦))↑2) = ((𝑁‘(𝐴𝐺𝐵))↑2))
38 oveq2 6612 . . . . . . . . 9 (𝑦 = 𝐵 → (-1𝑆𝑦) = (-1𝑆𝐵))
3938oveq2d 6620 . . . . . . . 8 (𝑦 = 𝐵 → (𝐴𝐺(-1𝑆𝑦)) = (𝐴𝐺(-1𝑆𝐵)))
4039fveq2d 6152 . . . . . . 7 (𝑦 = 𝐵 → (𝑁‘(𝐴𝐺(-1𝑆𝑦))) = (𝑁‘(𝐴𝐺(-1𝑆𝐵))))
4140oveq1d 6619 . . . . . 6 (𝑦 = 𝐵 → ((𝑁‘(𝐴𝐺(-1𝑆𝑦)))↑2) = ((𝑁‘(𝐴𝐺(-1𝑆𝐵)))↑2))
4237, 41oveq12d 6622 . . . . 5 (𝑦 = 𝐵 → (((𝑁‘(𝐴𝐺𝑦))↑2) + ((𝑁‘(𝐴𝐺(-1𝑆𝑦)))↑2)) = (((𝑁‘(𝐴𝐺𝐵))↑2) + ((𝑁‘(𝐴𝐺(-1𝑆𝐵)))↑2)))
43 fveq2 6148 . . . . . . . 8 (𝑦 = 𝐵 → (𝑁𝑦) = (𝑁𝐵))
4443oveq1d 6619 . . . . . . 7 (𝑦 = 𝐵 → ((𝑁𝑦)↑2) = ((𝑁𝐵)↑2))
4544oveq2d 6620 . . . . . 6 (𝑦 = 𝐵 → (((𝑁𝐴)↑2) + ((𝑁𝑦)↑2)) = (((𝑁𝐴)↑2) + ((𝑁𝐵)↑2)))
4645oveq2d 6620 . . . . 5 (𝑦 = 𝐵 → (2 · (((𝑁𝐴)↑2) + ((𝑁𝑦)↑2))) = (2 · (((𝑁𝐴)↑2) + ((𝑁𝐵)↑2))))
4742, 46eqeq12d 2636 . . . 4 (𝑦 = 𝐵 → ((((𝑁‘(𝐴𝐺𝑦))↑2) + ((𝑁‘(𝐴𝐺(-1𝑆𝑦)))↑2)) = (2 · (((𝑁𝐴)↑2) + ((𝑁𝑦)↑2))) ↔ (((𝑁‘(𝐴𝐺𝐵))↑2) + ((𝑁‘(𝐴𝐺(-1𝑆𝐵)))↑2)) = (2 · (((𝑁𝐴)↑2) + ((𝑁𝐵)↑2)))))
4834, 47rspc2v 3306 . . 3 ((𝐴𝑋𝐵𝑋) → (∀𝑥𝑋𝑦𝑋 (((𝑁‘(𝑥𝐺𝑦))↑2) + ((𝑁‘(𝑥𝐺(-1𝑆𝑦)))↑2)) = (2 · (((𝑁𝑥)↑2) + ((𝑁𝑦)↑2))) → (((𝑁‘(𝐴𝐺𝐵))↑2) + ((𝑁‘(𝐴𝐺(-1𝑆𝐵)))↑2)) = (2 · (((𝑁𝐴)↑2) + ((𝑁𝐵)↑2)))))
49483adant1 1077 . 2 ((𝑈 ∈ CPreHilOLD𝐴𝑋𝐵𝑋) → (∀𝑥𝑋𝑦𝑋 (((𝑁‘(𝑥𝐺𝑦))↑2) + ((𝑁‘(𝑥𝐺(-1𝑆𝑦)))↑2)) = (2 · (((𝑁𝑥)↑2) + ((𝑁𝑦)↑2))) → (((𝑁‘(𝐴𝐺𝐵))↑2) + ((𝑁‘(𝐴𝐺(-1𝑆𝐵)))↑2)) = (2 · (((𝑁𝐴)↑2) + ((𝑁𝐵)↑2)))))
5022, 49mpd 15 1 ((𝑈 ∈ CPreHilOLD𝐴𝑋𝐵𝑋) → (((𝑁‘(𝐴𝐺𝐵))↑2) + ((𝑁‘(𝐴𝐺(-1𝑆𝐵)))↑2)) = (2 · (((𝑁𝐴)↑2) + ((𝑁𝐵)↑2))))
Colors of variables: wff setvar class
Syntax hints:  wi 4  w3a 1036   = wceq 1480  wcel 1987  wral 2907  Vcvv 3186  cop 4154  cfv 5847  (class class class)co 6604  1st c1st 7111  2nd c2nd 7112  1c1 9881   + caddc 9883   · cmul 9885  -cneg 10211  2c2 11014  cexp 12800  NrmCVeccnv 27288   +𝑣 cpv 27289  BaseSetcba 27290   ·𝑠OLD cns 27291  normCVcnmcv 27294  CPreHilOLDccphlo 27516
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1719  ax-4 1734  ax-5 1836  ax-6 1885  ax-7 1932  ax-8 1989  ax-9 1996  ax-10 2016  ax-11 2031  ax-12 2044  ax-13 2245  ax-ext 2601  ax-rep 4731  ax-sep 4741  ax-nul 4749  ax-pow 4803  ax-pr 4867  ax-un 6902
This theorem depends on definitions:  df-bi 197  df-or 385  df-an 386  df-3an 1038  df-tru 1483  df-ex 1702  df-nf 1707  df-sb 1878  df-eu 2473  df-mo 2474  df-clab 2608  df-cleq 2614  df-clel 2617  df-nfc 2750  df-ne 2791  df-ral 2912  df-rex 2913  df-reu 2914  df-rab 2916  df-v 3188  df-sbc 3418  df-csb 3515  df-dif 3558  df-un 3560  df-in 3562  df-ss 3569  df-nul 3892  df-if 4059  df-sn 4149  df-pr 4151  df-op 4155  df-uni 4403  df-iun 4487  df-br 4614  df-opab 4674  df-mpt 4675  df-id 4989  df-xp 5080  df-rel 5081  df-cnv 5082  df-co 5083  df-dm 5084  df-rn 5085  df-res 5086  df-ima 5087  df-iota 5810  df-fun 5849  df-fn 5850  df-f 5851  df-f1 5852  df-fo 5853  df-f1o 5854  df-fv 5855  df-ov 6607  df-oprab 6608  df-1st 7113  df-2nd 7114  df-vc 27263  df-nv 27296  df-va 27299  df-ba 27300  df-sm 27301  df-0v 27302  df-nmcv 27304  df-ph 27517
This theorem is referenced by:  ip0i  27529  hlpar  27602
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