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Theorem symquadmid 29309
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 2760 . . . . . 6 (pInvG‘𝐺) = (pInvG‘𝐺)
6 symquadmid.g . . . . . . 7 (𝜑 → 𝐺 ∈ TarskiG)
76ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝐺 ∈ TarskiG)
8 eqid 2760 . . . . . 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 29099 . . . . . . . . 9 (𝜑 → 𝑋 ≠ 𝑍)
191, 3, 4, 6, 9, 13, 18tgelrnln 29103 . . . . . . . 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 29017 . . . . . 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 29092 . . . . . . 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 29166 . . . . 5 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑋 = (((pInvG‘𝐺)‘𝑡)‘𝑍))
351, 4, 3, 6, 11, 13, 9, 17ncoltgdim2 29033 . . . . . . 7 (𝜑 → 𝐺DimTarskiG≥2)
3635ad2antrr 739 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝐺DimTarskiG≥2)
371, 2, 3, 7, 36, 14, 10, 5, 22ismidb 29288 . . . . 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 29292 . . . 4 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋(midG‘𝐺)𝑍) = (𝑍(midG‘𝐺)𝑋))
401, 2, 3, 7, 36, 12, 16midcom 29292 . . . . 5 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑌(midG‘𝐺)𝑊) = (𝑊(midG‘𝐺)𝑌))
4128eqcomd 2766 . . . . . . . . . . . . 13 (𝜑 → (𝑊 − 𝑋) = (𝑌 − 𝑍))
421, 2, 3, 6, 15, 9, 11, 13, 41tgcgrcomlr 28947 . . . . . . . . . . . 12 (𝜑 → (𝑋 − 𝑊) = (𝑍 − 𝑌))
4342eqcomd 2766 . . . . . . . . . . 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 28947 . . . . . . . . . . 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 29031 . . . . . . . . . . . 12 (𝜑 → ¬ (𝑍 ∈ (𝑋𝐿𝑌) ∨ 𝑋 = 𝑌))
481, 4, 3, 6, 9, 11, 13, 47ncolcom 29029 . . . . . . . . . . 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 29108 . . . . . . . . . . . 12 (𝜑 → (𝑋𝐿𝑍) = (𝑍𝐿𝑋))
5150ad2antrr 739 . . . . . . . . . . 11 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋𝐿𝑍) = (𝑍𝐿𝑋))
5221, 51eleqtrd 2862 . . . . . . . . . 10 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑡 ∈ (𝑍𝐿𝑋))
531, 2, 4, 7, 14, 12, 10, 16, 44, 46, 49, 25, 52, 32symquadprlnglem 29170 . . . . . . . . 9 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → ¬ (𝑊 ∈ (𝑋𝐿𝑌) ∨ 𝑋 = 𝑌))
541, 4, 3, 7, 10, 12, 16, 53ncolcom 29029 . . . . . . . 8 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → ¬ (𝑊 ∈ (𝑌𝐿𝑋) ∨ 𝑌 = 𝑋))
551, 4, 3, 7, 12, 10, 16, 54ncolrot1 29030 . . . . . . 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 29166 . . . . . 6 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → 𝑌 = (((pInvG‘𝐺)‘𝑡)‘𝑊))
591, 2, 3, 7, 36, 16, 12, 5, 22ismidb 29288 . . . . . 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 2795 . . . 4 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑌(midG‘𝐺)𝑊) = 𝑡)
6238, 39, 613eqtr4d 2805 . . 3 (((𝜑 ∧ 𝑡 ∈ (𝑋𝐿𝑍)) ∧ 𝑡 ∈ (𝑌𝐼𝑊)) → (𝑋(midG‘𝐺)𝑍) = (𝑌(midG‘𝐺)𝑊))
63 symquadmid.m . . . 4 𝑀 = (midG‘𝐺)
6463oveqi 7433 . . 3 (𝑋𝑀𝑍) = (𝑋(midG‘𝐺)𝑍)
6563oveqi 7433 . . 3 (𝑌𝑀𝑊) = (𝑌(midG‘𝐺)𝑊)
6662, 64, 653eqtr4g 2820 . 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 29220 . . . 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 3170 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 1569   ∈ wcel 2144   ≠ wne 2955  ∃wrex 3086   ∖ cdif 4045   class class class wbr 5102  {copab 5166  ran crn 5651  ‘cfv 6538  (class class class)co 7420  2c2 12400  Basecbs 17392  distcds 17442  TarskiGcstrkg 28894  DimTarskiG≥cstrkgld 28898  Itvcitv 28900  LineGclng 28901  pInvGcmir 29129  midGcmid 29282
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 7751  ax-cnex 11259  ax-resscn 11260  ax-1cn 11261  ax-icn 11262  ax-addcl 11263  ax-addrcl 11264  ax-mulcl 11265  ax-mulrcl 11266  ax-mulcom 11267  ax-addass 11268  ax-mulass 11269  ax-distr 11270  ax-i2m1 11271  ax-1ne0 11272  ax-1rid 11273  ax-rnegex 11274  ax-rrecex 11275  ax-cnre 11276  ax-pre-lttri 11277  ax-pre-lttrn 11278  ax-pre-ltadd 11279  ax-pre-mulgt0 11280
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 3847  df-ss 3896  df-pss 4014  df-dif 4047  df-in 4091  df-un 4151  df-nul 4279  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-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-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 6304  df-ord 6365  df-on 6366  df-lim 6367  df-suc 6368  df-iota 6494  df-fun 6540  df-fn 6541  df-f 6542  df-f1 6543  df-fo 6544  df-f1o 6545  df-fv 6546  df-riota 7377  df-ov 7423  df-oprab 7424  df-mpo 7425  df-om 7878  df-1st 8001  df-2nd 8002  df-frecs 8302  df-wrecs 8333  df-recs 8382  df-rdg 8421  df-1o 8479  df-oadd 8483  df-er 8720  df-map 8852  df-pm 8853  df-en 8977  df-dom 8978  df-sdom 8979  df-fin 8980  df-dju 9985  df-card 10023  df-pnf 11348  df-mnf 11349  df-xr 11350  df-ltxr 11351  df-le 11352  df-sub 11546  df-neg 11547  df-nn 12339  df-2 12408  df-3 12409  df-n0 12610  df-xnn0 12683  df-z 12697  df-uz 12969  df-fz 13643  df-fzo 13792  df-hash 14478  df-word 14662  df-concat 14719  df-s1 14746  df-s2 15003  df-s3 15004  df-trkgc 28915  df-trkgb 28916  df-trkgcb 28917  df-trkgld 28919  df-trkg 28920  df-cgrg 28979  df-leg 29051  df-mir 29130  df-rag 29174  df-perpg 29176  df-mid 29284
This theorem is used by: (None)
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