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Theorem symquadmid 29286
Description: In a symmetrical quadrilateral, the midpoints of the diagonals coincide. Corollary of Lemma 7.21 of [Schwabhauser] p. 52. (Contributed by Thierry Arnoux, 20-Jul-2026.)
Hypotheses
Ref Expression
symquadmid.p 𝑃 = (Base‘𝐺)
symquadmid.d − = (dist‘𝐺)
symquadmid.i 𝐼 = (Itv‘𝐺)
symquadmid.l 𝐿 = (LineG‘𝐺)
symquadmid.m 𝑀 = (midG‘𝐺)
symquadmid.o 𝑂 = {⟨𝑎, 𝑏⟩ ∣ ((𝑎 ∈ (𝑃 ∖ (𝑋𝐿𝑍)) ∧ 𝑏 ∈ (𝑃 ∖ (𝑋𝐿𝑍))) ∧ ∃𝑡 ∈ (𝑋𝐿𝑍)𝑡 ∈ (𝑎𝐼𝑏))}
symquadmid.g (𝜑 → 𝐺 ∈ TarskiG)
symquadmid.x (𝜑 → 𝑋 ∈ 𝑃)
symquadmid.y (𝜑 → 𝑌 ∈ 𝑃)
symquadmid.z (𝜑 → 𝑍 ∈ 𝑃)
symquadmid.w (𝜑 → 𝑊 ∈ 𝑃)
symquadmid.2 (𝜑 → ¬ (𝑋 ∈ (𝑌𝐿𝑍) ∨ 𝑌 = 𝑍))
symquadmid.3 (𝜑 → 𝑌 ≠ 𝑊)
symquadmid.4 (𝜑 → (𝑋 − 𝑌) = (𝑍 − 𝑊))
symquadmid.5 (𝜑 → (𝑌 − 𝑍) = (𝑊 − 𝑋))
symquadmid.6 (𝜑 → 𝑌𝑂𝑊)
Assertion
Ref Expression
symquadmid (𝜑 → (𝑋𝑀𝑍) = (𝑌𝑀𝑊))
Distinct variable groups:   𝐼,𝑎,𝑏   𝐿,𝑎,𝑏   𝑡,𝑀   𝑃,𝑎,𝑏   𝑡,𝑊   𝑋,𝑎,𝑏,𝑡   𝑡,𝑌   𝑍,𝑎,𝑏,𝑡   𝜑,𝑡
Allowed substitution hints:   𝜑(𝑎, 𝑏)   𝑃(𝑡)   𝐺(𝑡, 𝑎, 𝑏)   𝐼(𝑡)   𝐿(𝑡)   𝑀(𝑎, 𝑏)   − (𝑡, 𝑎, 𝑏)   𝑂(𝑡, 𝑎, 𝑏)   𝑊(𝑎, 𝑏)   𝑌(𝑎, 𝑏)

Proof of Theorem symquadmid
StepHypRef Expression
1 symquadmid.p . . . . . 6 𝑃 = (Base‘𝐺)
2 symquadmid.d . . . . . 6 − = (dist‘𝐺)
3 symquadmid.i . . . . . 6 𝐼 = (Itv‘𝐺)
4 symquadmid.l . . . . . 6 𝐿 = (LineG‘𝐺)
5 eqid 2761 . . . . . 6 (pInvG‘𝐺) = (pInvG‘𝐺)
6 symquadmid.g . . . . . . 7 (𝜑 → 𝐺 ∈ TarskiG)
76ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝐺 ∈ TarskiG)
8 eqid 2761 . . . . . 6 ((pInvG‘𝐺)‘𝑡) = ((pInvG‘𝐺)‘𝑡)
9 symquadmid.x . . . . . . 7 (𝜑 → 𝑋 ∈ 𝑃)
109ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑋 ∈ 𝑃)
11 symquadmid.y . . . . . . 7 (𝜑 → 𝑌 ∈ 𝑃)
1211ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑌 ∈ 𝑃)
13 symquadmid.z . . . . . . 7 (𝜑 → 𝑍 ∈ 𝑃)
1413ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑍 ∈ 𝑃)
15 symquadmid.w . . . . . . 7 (𝜑 → 𝑊 ∈ 𝑃)
1615ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑊 ∈ 𝑃)
17 symquadmid.2 . . . . . . . . . 10 (𝜑 → ¬ (𝑋 ∈ (𝑌𝐿𝑍) ∨ 𝑌 = 𝑍))
181, 3, 4, 6, 9, 11, 13, 17ncolne2 29076 . . . . . . . . 9 (𝜑 → 𝑋 ≠ 𝑍)
191, 3, 4, 6, 9, 13, 18tgelrnln 29080 . . . . . . . 8 (𝜑 → (𝑋𝐿𝑍) ∈ ran 𝐿)
2019ad2antrr 739 . . . . . . 7 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋𝐿𝑍) ∈ ran 𝐿)
21 simplr 781 . . . . . . 7 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑡 ∈ (𝑋𝐿𝑍))
221, 4, 3, 7, 20, 21tglnpt 28994 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑡 ∈ 𝑃)
2317ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → ¬ (𝑋 ∈ (𝑌𝐿𝑍) ∨ 𝑌 = 𝑍))
24 symquadmid.3 . . . . . . 7 (𝜑 → 𝑌 ≠ 𝑊)
2524ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑌 ≠ 𝑊)
26 symquadmid.4 . . . . . . 7 (𝜑 → (𝑋 − 𝑌) = (𝑍 − 𝑊))
2726ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋 − 𝑌) = (𝑍 − 𝑊))
28 symquadmid.5 . . . . . . 7 (𝜑 → (𝑌 − 𝑍) = (𝑊 − 𝑋))
2928ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑌 − 𝑍) = (𝑊 − 𝑋))
3021orcd 887 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑡 ∈ (𝑋𝐿𝑍) ∨ 𝑋 = 𝑍))
31 simpr 490 . . . . . . . 8 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑡 ∈ (𝑌𝐼𝑊))
321, 3, 4, 7, 12, 16, 22, 25, 31btwnlng1 29069 . . . . . . 7 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑡 ∈ (𝑌𝐿𝑊))
3332orcd 887 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑡 ∈ (𝑌𝐿𝑊) ∨ 𝑌 = 𝑊))
341, 2, 3, 4, 5, 7, 8, 10, 12, 14, 16, 22, 23, 25, 27, 29, 30, 33symquadlem 29143 . . . . 5 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑋 = (((pInvG‘𝐺)‘𝑡)‘𝑍))
351, 4, 3, 6, 11, 13, 9, 17ncoltgdim2 29010 . . . . . . 7 (𝜑 → 𝐺DimTarskiG≥2)
3635ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝐺DimTarskiG≥2)
371, 2, 3, 7, 36, 14, 10, 5, 22ismidb 29265 . . . . 5 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋 = (((pInvG‘𝐺)‘𝑡)‘𝑍) ↔ (𝑍(midG‘𝐺)𝑋) = 𝑡))
3834, 37mpbid 235 . . . 4 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑍(midG‘𝐺)𝑋) = 𝑡)
391, 2, 3, 7, 36, 10, 14midcom 29269 . . . 4 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋(midG‘𝐺)𝑍) = (𝑍(midG‘𝐺)𝑋))
401, 2, 3, 7, 36, 12, 16midcom 29269 . . . . 5 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑌(midG‘𝐺)𝑊) = (𝑊(midG‘𝐺)𝑌))
4128eqcomd 2767 . . . . . . . . . . . . 13 (𝜑 → (𝑊 − 𝑋) = (𝑌 − 𝑍))
421, 2, 3, 6, 15, 9, 11, 13, 41tgcgrcomlr 28924 . . . . . . . . . . . 12 (𝜑 → (𝑋 − 𝑊) = (𝑍 − 𝑌))
4342eqcomd 2767 . . . . . . . . . . 11 (𝜑 → (𝑍 − 𝑌) = (𝑋 − 𝑊))
4443ad2antrr 739 . . . . . . . . . 10 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑍 − 𝑌) = (𝑋 − 𝑊))
451, 2, 3, 6, 9, 11, 13, 15, 26tgcgrcomlr 28924 . . . . . . . . . . 11 (𝜑 → (𝑌 − 𝑋) = (𝑊 − 𝑍))
4645ad2antrr 739 . . . . . . . . . 10 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑌 − 𝑋) = (𝑊 − 𝑍))
471, 4, 3, 6, 11, 13, 9, 17ncolrot2 29008 . . . . . . . . . . . 12 (𝜑 → ¬ (𝑍 ∈ (𝑋𝐿𝑌) ∨ 𝑋 = 𝑌))
481, 4, 3, 6, 9, 11, 13, 47ncolcom 29006 . . . . . . . . . . 11 (𝜑 → ¬ (𝑍 ∈ (𝑌𝐿𝑋) ∨ 𝑌 = 𝑋))
4948ad2antrr 739 . . . . . . . . . 10 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → ¬ (𝑍 ∈ (𝑌𝐿𝑋) ∨ 𝑌 = 𝑋))
501, 3, 4, 6, 9, 13, 18tglinecom 29085 . . . . . . . . . . . 12 (𝜑 → (𝑋𝐿𝑍) = (𝑍𝐿𝑋))
5150ad2antrr 739 . . . . . . . . . . 11 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋𝐿𝑍) = (𝑍𝐿𝑋))
5221, 51eleqtrd 2863 . . . . . . . . . 10 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑡 ∈ (𝑍𝐿𝑋))
531, 2, 4, 7, 14, 12, 10, 16, 44, 46, 49, 25, 52, 32symquadprlnglem 29147 . . . . . . . . 9 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → ¬ (𝑊 ∈ (𝑋𝐿𝑌) ∨ 𝑋 = 𝑌))
541, 4, 3, 7, 10, 12, 16, 53ncolcom 29006 . . . . . . . 8 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → ¬ (𝑊 ∈ (𝑌𝐿𝑋) ∨ 𝑌 = 𝑋))
551, 4, 3, 7, 12, 10, 16, 54ncolrot1 29007 . . . . . . 7 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → ¬ (𝑌 ∈ (𝑋𝐿𝑊) ∨ 𝑋 = 𝑊))
5618ad2antrr 739 . . . . . . 7 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑋 ≠ 𝑍)
5742ad2antrr 739 . . . . . . 7 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋 − 𝑊) = (𝑍 − 𝑌))
581, 2, 3, 4, 5, 7, 8, 12, 10, 16, 14, 22, 55, 56, 46, 57, 33, 30symquadlem 29143 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑌 = (((pInvG‘𝐺)‘𝑡)‘𝑊))
591, 2, 3, 7, 36, 16, 12, 5, 22ismidb 29265 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑌 = (((pInvG‘𝐺)‘𝑡)‘𝑊) ↔ (𝑊(midG‘𝐺)𝑌) = 𝑡))
6058, 59mpbid 235 . . . . 5 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑊(midG‘𝐺)𝑌) = 𝑡)
6140, 60eqtrd 2796 . . . 4 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑌(midG‘𝐺)𝑊) = 𝑡)
6238, 39, 613eqtr4d 2806 . . 3 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋(midG‘𝐺)𝑍) = (𝑌(midG‘𝐺)𝑊))
63 symquadmid.m . . . 4 𝑀 = (midG‘𝐺)
6463oveqi 7425 . . 3 (𝑋𝑀𝑍) = (𝑋(midG‘𝐺)𝑍)
6563oveqi 7425 . . 3 (𝑌𝑀𝑊) = (𝑌(midG‘𝐺)𝑊)
6662, 64, 653eqtr4g 2821 . 2 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋𝑀𝑍) = (𝑌𝑀𝑊))
67 symquadmid.6 . . . 4 (𝜑 → 𝑌𝑂𝑊)
68 symquadmid.o . . . . 5 𝑂 = {⟨𝑎, 𝑏⟩ ∣ ((𝑎 ∈ (𝑃 ∖ (𝑋𝐿𝑍)) ∧ 𝑏 ∈ (𝑃 ∖ (𝑋𝐿𝑍))) ∧ ∃𝑡 ∈ (𝑋𝐿𝑍)𝑡 ∈ (𝑎𝐼𝑏))}
691, 2, 3, 68, 11, 15islnopp 29197 . . . 4 (𝜑 → (𝑌𝑂𝑊 ↔ ((¬ 𝑌 ∈ (𝑋𝐿𝑍) ∧ ¬ 𝑊 ∈ (𝑋𝐿𝑍)) ∧ ∃𝑡 ∈ (𝑋𝐿𝑍)𝑡 ∈ (𝑌𝐼𝑊))))
7067, 69mpbid 235 . . 3 (𝜑 → ((¬ 𝑌 ∈ (𝑋𝐿𝑍) ∧ ¬ 𝑊 ∈ (𝑋𝐿𝑍)) ∧ ∃𝑡 ∈ (𝑋𝐿𝑍)𝑡 ∈ (𝑌𝐼𝑊)))
7170simprd 501 . 2 (𝜑 → ∃𝑡 ∈ (𝑋𝐿𝑍)𝑡 ∈ (𝑌𝐼𝑊))
7266, 71r19.29a 3171 1 (𝜑 → (𝑋𝑀𝑍) = (𝑌𝑀𝑊))
Colors of variables:    wff setvar class
This proof depends on syntax axioms:  ¬ wn 3   → wi 4   ∧ wa 401   ∨ wo 861   = wceq 1570   ∈ wcel 2145   ≠ wne 2956  ∃wrex 3087   ∖ cdif 3896   class class class wbr 5103  {copab 5167  ran crn 5652  ‘cfv 6531  (class class class)co 7412  2c2 12378  Basecbs 17367  distcds 17417  TarskiGcstrkg 28871  DimTarskiG≥cstrkgld 28875  Itvcitv 28877  LineGclng 28878  pInvGcmir 29106  midGcmid 29259
This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041  ax-8 2147  ax-9 2155  ax-10 2178  ax-11 2194  ax-12 2213  ax-ext 2733  ax-rep 5232  ax-sep 5249  ax-nul 5260  ax-pow 5327  ax-pr 5391  ax-un 7740  ax-cnex 11237  ax-resscn 11238  ax-1cn 11239  ax-icn 11240  ax-addcl 11241  ax-addrcl 11242  ax-mulcl 11243  ax-mulrcl 11244  ax-mulcom 11245  ax-addass 11246  ax-mulass 11247  ax-distr 11248  ax-i2m1 11249  ax-1ne0 11250  ax-1rid 11251  ax-rnegex 11252  ax-rrecex 11253  ax-cnre 11254  ax-pre-lttri 11255  ax-pre-lttrn 11256  ax-pre-ltadd 11257  ax-pre-mulgt0 11258
This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-3or 1104  df-3an 1105  df-tru 1573  df-fal 1583  df-ex 1813  df-nf 1817  df-sb 2100  df-mo 2565  df-eu 2595  df-clab 2740  df-cleq 2753  df-clel 2836  df-nfc 2910  df-ne 2957  df-nel 3063  df-ral 3078  df-rex 3088  df-rmo 3366  df-reu 3367  df-rab 3414  df-v 3453  df-sbc 3740  df-csb 3848  df-dif 3902  df-un 3904  df-in 3906  df-ss 3916  df-pss 3919  df-nul 4280  df-if 4483  df-pw 4559  df-sn 4585  df-pr 4587  df-tp 4589  df-op 4591  df-uni 4868  df-int 4908  df-iun 4953  df-br 5104  df-opab 5168  df-mpt 5187  df-tr 5213  df-id 5546  df-eprel 5551  df-po 5559  df-so 5560  df-fr 5604  df-we 5606  df-xp 5657  df-rel 5658  df-cnv 5659  df-co 5660  df-dm 5661  df-rn 5662  df-res 5663  df-ima 5664  df-pred 6297  df-ord 6358  df-on 6359  df-lim 6360  df-suc 6361  df-iota 6487  df-fun 6533  df-fn 6534  df-f 6535  df-f1 6536  df-fo 6537  df-f1o 6538  df-fv 6539  df-riota 7369  df-ov 7415  df-oprab 7416  df-mpo 7417  df-om 7867  df-1st 7990  df-2nd 7991  df-frecs 8283  df-wrecs 8314  df-recs 8363  df-rdg 8402  df-1o 8460  df-oadd 8464  df-er 8701  df-map 8833  df-pm 8834  df-en 8958  df-dom 8959  df-sdom 8960  df-fin 8961  df-dju 9963  df-card 10001  df-pnf 11326  df-mnf 11327  df-xr 11328  df-ltxr 11329  df-le 11330  df-sub 11524  df-neg 11525  df-nn 12317  df-2 12386  df-3 12387  df-n0 12588  df-xnn0 12661  df-z 12675  df-uz 12947  df-fz 13621  df-fzo 13769  df-hash 14455  df-word 14639  df-concat 14696  df-s1 14723  df-s2 14979  df-s3 14980  df-trkgc 28892  df-trkgb 28893  df-trkgcb 28894  df-trkgld 28896  df-trkg 28897  df-cgrg 28956  df-leg 29028  df-mir 29107  df-rag 29151  df-perpg 29153  df-mid 29261
This theorem is used by: (None)
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