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Statement List for Metamath Proof Explorer - 3301-3400 - Page 34 of 58
TypeLabelDescription
Statement
 
Theoremf1oen 3301 The domain and range of a one-to-one, onto function are equinumerous.
AV    ⇒   (F:A1-1-ontoBAB)
 
Theoremf1dom 3302 The domain of a one-to-one function is dominated by its range.
AV    ⇒   (F:A1-1BAB)
 
Theoremen2d 3303 Equinumerosity inference from an implicit one-to-one onto function.
(φAV)    &   (φ → (xACV))    &   (φ → (yBDV))    &   (φ → ((xAy = C) ↔ (yBx = D)))    ⇒   (φAB)
 
Theoremen3d 3304 Equinumerosity inference from an implicit one-to-one onto function.
(φAV)    &   (φ → (xACB))    &   (φ → (yBDA))    &   (φ → ((xAyB) → (x = Dy = C)))    ⇒   (φAB)
 
Theoremen2 3305 Equinumerosity inference from an implicit one-to-one onto function.
AV    &   (xACV)    &   (yBDV)    &   ((xAy = C) ↔ (yBx = D))    ⇒   AB
 
Theoremen3 3306 Equinumerosity inference from an implicit one-to-one onto function.
AV    &   (xACB)    &   (yBDA)    &   ((xAyB) → (x = Dy = C))    ⇒   AB
 
Theoremdom2d 3307 A mapping (first hypothesis) that is one-to-one (second hypothesis) implies its domain is dominated by its range.
(φ → (xACB))    &   (φ → ((xAyA) → (C = Dx = y)))    ⇒   (φ → (ARAB))
 
Theoremdom2 3308 A mapping (first hypothesis) that is one-to-one (second hypothesis) implies its domain is dominated by its range.
(xACB)    &   ((xAyA) → (C = Dx = y))    ⇒   (ARAB)
 
Theoremidssen 3309 Equality implies equinumerosity.
I ⊆ ≈
 
Theoremdmen 3310 The domain of equinumerosity.
dom ≈ = V
 
Theoremssdomg 3311 A set dominates its subsets. Theorem 16 of [Suppes] p. 94.
(AC → (ABAB))
 
Theoremssdom2g 3312 A set dominates its subsets. Theorem 16 of [Suppes] p. 94.
(BC → (ABAB))
 
Theoremener 3313 Equinumerosity is an equivalence relation.
Er ≈
 
Theoremsdomirr 3314 Strict dominance is irreflexive. Theorem 21(i) of [Suppes] p. 97.
¬ AA
 
Theoremsdomex 3315 Technical lemma for simplifying proofs involving strict dominance.
(AB → (AVBV))
 
Theoremensymg 3316 Symmetry of equinumerosity. Theorem 2 of [Suppes] p. 92.
(BC → (ABBA))
 
Theoremensym 3317 Symmetry of equinumerosity. Theorem 2 of [Suppes] p. 92.
BV    ⇒   (ABBA)
 
Theoremensymi 3318 Symmetry of equinumerosity. Theorem 2 of [Suppes] p. 92.
BV    &   AB    ⇒   BA
 
Theorementrt 3319 Transitivity of equinumerosity. Theorem 3 of [Suppes] p. 92.
((ABBC) → AC)
 
Theoremdomtr 3320 Transitivity of dominance relation. Theorem 17 of [Suppes] p. 94.
((ABBC) → AC)
 
Theorementr 3321 A chained equinumerosity inference.
AB    &   BC    ⇒   AC
 
Theorementr2 3322 A chained equinumerosity inference.
CV    &   AB    &   BC    ⇒   CA
 
Theorementr3 3323 A chained equinumerosity inference.
BV    &   AB    &   AC    ⇒   BC
 
Theorementr4 3324 A chained equinumerosity inference.
BV    &   AB    &   CB    ⇒   AC
 
Theoremendomtr 3325 Transitivity of equinumerosity and dominance.
((ABBC) → AC)
 
Theoremdomentr 3326 Transitivity of dominance and equinumerosity.
((ABBC) → AC)
 
Theoremf1imaen 3327 A one-to-one function's image under a subset of its domain is equinumerous to the subset.
CV    ⇒   ((F:A1-1BCA) → (FC) ≈ C)
 
Theoremen0 3328 The empty set is equinumerous only to itself. Exercise 1 of [TakeutiZaring] p. 88.
(A ≈ ∅ ↔ A = ∅)
 
Theoremensn1 3329 A singleton is equinumerous to ordinal one.
AV    ⇒   {A} ≈ 1o
 
Theoremensn1g 3330 A singleton is equinumerous to ordinal one.
(AB → {A} ≈ 1o)
 
Theoremen1 3331 A set is equinumerous to ordinal one iff it is a singleton.
(A ≈ 1o ↔ ∃x A = {x})
 
Theorem2dom 3332 A set that dominates ordinal 2 has at least 2 different members.
AV    ⇒   (2oA → ∃xAyA ¬ x = y)
 
Theoremfundmen 3333 A function is equinumerous to its domain. Exercise 4 of [Suppes] p. 98.
FV    ⇒   (Fun F → dom FF)
 
Theoremmapsnen 3334 Set exponentiation to a singleton exponent is equinumerous to its base. Exercise 4.43 of [Mendelson] p. 255.
AV    &   BV    ⇒   (Am {B}) ≈ A
 
Theoremmap1 3335 Set exponentiation: ordinal 1 to any set is equinumerous to ordinal 1. Exercise 4.42(b) of [Mendelson] p. 255.
AV    ⇒   (1om A) ≈ 1o
 
Theoremen2sn 3336 Two singletons are equinumerous.
((ACBD) → {A} ≈ {B})
 
Theoremsnfi 3337 A singleton is finite.
x ∈ ω {A} ≈ x
 
Theoremunen 3338 Equinumerosity of union of disjoint sets. Theorem 4 of [Suppes] p. 92.
(((ABCD) ∧ ((AC) = ∅ ∧ (BD) = ∅)) → (AC) ≈ (BD))
 
Theoremxpsnen 3339 A set is equinumerous to its cross-product with a singleton. Proposition 4.22(c) of [Mendelson] p. 254.
AV    &   BV    ⇒   (A × {B}) ≈ A
 
Theoremxpsneng 3340 A set is equinumerous to its cross-product with a singleton. Proposition 4.22(c) of [Mendelson] p. 254.
((ACBD) → (A × {B}) ≈ A)
 
Theoremendisj 3341 Any two sets are equinumerous to disjoint sets. Exercise 4.39 of [Mendelson] p. 255.
AV    &   BV    ⇒   xy((xAyB) ∧ (xy) = ∅)
 
Theoremundom 3342 Dominance law for union. Proposition 4.24(a) of [Mendelson] p. 257.
BV    &   CV    &   DV    ⇒   (((ABCD) ∧ (BD) = ∅) → (AC) ≼ (BD))
 
Theoremxpcomen 3343 Commutative law for equinumerosity of cross product. Proposition 4.22(d) of [Mendelson] p. 254.
AV    &   BV    ⇒   (A × B) ≈ (B × A)
 
Theoremxpassen 3344 Associative law for equinumerosity of cross product. Proposition 4.22(e) of [Mendelson] p. 254.
AV    &   BV    &   CV    ⇒   ((A × B) × C) ≈ (A × (B × C))
 
Theoremxpdom2 3345 Dominance law for cross product. Proposition 10.33(2) of [TakeutiZaring] p. 92.
AV    &   BV    &   CV    ⇒   (AB → (C × A) ≼ (C × B))
 
Theoremxpdom1 3346 Dominance law for cross product. Theorem 6L(c) of [Enderton] p. 149.
AV    &   BV    &   CV    ⇒   (AB → (A × C) ≼ (B × C))
 
Theoremxpdom3 3347 A set is dominated by its cross product with a non-empty set. Exercise 6 of [Suppes] p. 98.
AV    ⇒   B = ∅ → A ≼ (A × B))
 
Theorempw2en 3348 The power set of a set is equinumerous to set exponentiation with a base of ordinal 2. Proposition 10.44 of [TakeutiZaring] p. 96. (This proof seems excessively long. An attempt to find a shorter one is on my to-do list.)
AV    ⇒   A ≈ (2om A)
 
Theoremsbthlem1 3349 Lemma for Schroeder-Bernstein Theorem.
AV    &   D = {x∣(xA ∧ (g “ (B ∖ (fx))) ⊆ (Ax))}    ⇒   D ⊆ (A ∖ (g “ (B ∖ (fD))))
 
Theoremsbthlem2 3350 Lemma for Schroeder-Bernstein Theorem.
AV    &   D = {x∣(xA ∧ (g “ (B ∖ (fx))) ⊆ (Ax))}    ⇒   (ran gA → (A ∖ (g “ (B ∖ (fD)))) ⊆ D)
 
Theoremsbthlem3 3351 Lemma for Schroeder-Bernstein Theorem.
AV    &   D = {x∣(xA ∧ (g “ (B ∖ (fx))) ⊆ (Ax))}    ⇒   (ran gA → (g “ (B ∖ (fD))) = (AD))
 
Theoremsbthlem4 3352 Lemma for Schroeder-Bernstein Theorem.
AV    &   D = {x∣(xA ∧ (g “ (B ∖ (fx))) ⊆ (Ax))}    ⇒   (((dom g = B ∧ ran gA) ∧ Fun g) → (g “ (AD)) = (B ∖ (fD)))
 
Theoremsbthlem5 3353 Lemma for Schroeder-Bernstein Theorem.
AV    &   D = {x∣(xA ∧ (g “ (B ∖ (fx))) ⊆ (Ax))}    &   H = ((fD) ∪ (g ↾ (AD)))    ⇒   ((dom f = A ∧ ran gA) → dom H = A)
 
Theoremsbthlem6 3354 Lemma for Schroeder-Bernstein Theorem.
AV    &   D = {x∣(xA ∧ (g “ (B ∖ (fx))) ⊆ (Ax))}    &   H = ((fD) ∪ (g ↾ (AD)))    ⇒   ((ran fB ∧ ((dom g = B ∧ ran gA) ∧ Fun g)) → ran H = B)
 
Theoremsbthlem7 3355 Lemma for Schroeder-Bernstein Theorem.
AV    &   D = {x∣(xA ∧ (g “ (B ∖ (fx))) ⊆ (Ax))}    &   H = ((fD) ∪ (g ↾ (AD)))    ⇒   ((Fun f ∧ Fun g) → Fun H)
 
Theoremsbthlem8 3356 Lemma for Schroeder-Bernstein Theorem.
AV    &   D = {x∣(xA ∧ (g “ (B ∖ (fx))) ⊆ (Ax))}    &   H = ((fD) ∪ (g ↾ (AD)))    ⇒   ((Fun f ∧ (((Fun g ∧ dom g = B) ∧ ran gA) ∧ Fun g)) → Fun H)
 
Theoremsbthlem9 3357 Lemma for Schroeder-Bernstein Theorem.
AV    &   D = {x∣(xA ∧ (g “ (B ∖ (fx))) ⊆ (Ax))}    &   H = ((fD) ∪ (g ↾ (AD)))    ⇒   ((f:A1-1Bg:B1-1A) → H:A1-1-ontoB)
 
Theoremsbthlem10 3358 Lemma for Schroeder-Bernstein Theorem.
AV    &   D = {x∣(xA ∧ (g “ (B ∖ (fx))) ⊆ (Ax))}    &   H = ((fD) ∪ (g ↾ (AD)))    &   BV    ⇒   ((ABBA) → AB)
 
Theoremsbth 3359 Schroeder-Bernstein Theorem. Theorem 18 of [Suppes] p. 95. This theorem states that if set A is smaller (has lower cardinality) than B and vice-versa, then A and B are equinumerous (have the same cardinality). The interesting thing is that this can be proved without invoking the Axiom of Choice, as we do here, but the proof as you can see is quite difficult. (The theorem can be proved more easily if we allow AC.) The main proof consists of lemmas sbthlem1 3349 through sbthlem10 3358; this final piece mainly changes bound variables to eliminate the hypotheses of sbthlem10 3358. We closely follow the proof in Suppes, which you should consult to understand our proof at a higher level.
((ABBA) → AB)
 
Theoremsbthbg 3360 Schroeder-Bernstein Theorem and its converse.
(BC → ((ABBA) ↔ AB))
 
Theoremsbthcl 3361 Schroeder-Bernstein Theorem in class form.
≈ = ( ≼ ∩ ≼ )
 
Theoremdfsdom2 3362 Alternate definition of strict dominance. Compare Definition 3 of [Suppes] p. 97.
≺ = ( ≼ ∖ ≼ )
 
Theorembrsdom2 3363 Alternate definition of strict dominance. Definition 3 of [Suppes] p. 97.
AV    &   BV    ⇒   (AB ↔ (AB ∧ ¬ BA))
 
Theoremsdomnsym 3364 Strict dominance is not symmetric. Theorem 21(ii) of [Suppes] p. 97.
(AB → ¬ BA)
 
Theoremdomnsym 3365 Theorem 22(i) of [Suppes] p. 97.
(AB → ¬ BA)
 
Theorem0dom 3366 Any set dominates the empty set.
∅ ≼ A
 
Theoremdom0 3367 A set dominated by the empty set is empty.
(A ≼ ∅ ↔ A = ∅)
 
Theorem0sdom 3368 A set strictly dominates the empty set iff it is not empty.
AV    ⇒   (∅ ≺ A ↔ ¬ A = ∅)
 
Theoremsdom0 3369 The empty set does not strictly dominate any set.
¬ A ≺ ∅
 
Theoremsdomdomtr 3370 Transitivity of strict dominance and dominance. Theorem 22(iii) of [Suppes] p. 97.
(CD → ((ABBC) → AC))
 
Theoremsdomentr 3371 Transitivity of strict dominance and equinumerosity. Exercise 11 of [Suppes] p. 98.
(CD → ((ABBC) → AC))
 
Theoremensdomtr 3372 Transitivity of equinumerosity and strict dominance.
((ABBC) → AC)
 
Theoremsdomtr 3373 Strict dominance is transitive. Theorem 21(iii) of [Suppes] p. 97.
((ABBC) → AC)
 
Theoremdomsdomtr 3374 Transitivity of dominance and strict dominance. Theorem 22(ii) of [Suppes] p. 97.
((ABBC) → AC)
 
Theoremenen1 3375 Equality-like theorem for equinumerosity.
((BDAB) → (ACBC))
 
Theoremenen2 3376 Equality-like theorem for equinumerosity.
((BDAB) → (CACB))
 
Theoremdomen1 3377 Equality-like theorem for equinumerosity and dominance.
((BDAB) → (ACBC))
 
Theoremdomen2 3378 Equality-like theorem for equinumerosity and dominance.
((BDAB) → (CACB))
 
Theoremsdomen1 3379 Equality-like theorem for equinumerosity and strict dominance.
((BDAB) → (ACBC))
 
Theoremsdomen2 3380 Equality-like theorem for equinumerosity and strict dominance.
((BDAB) → (CACB))
 
Theoremcanth2 3381 Cantor's Theorem. No set is equinumerous to its power set. Specifically, any set has a cardinality (size) strictly less than the cardinality of its power set. For example, the cardinality of real numbers is the same as the cardinality of the power set of integers, so real numbers cannot be put into a one-to-one correspondence with integers. Theorem 23 of [Suppes] p. 97. For the function version, see canth 2945.
AV    ⇒   A ≺ ℘A
 
Theoremcanth2g 3382 Cantor's theorem with the sethood requirement expressed as an antecedent. Theorem 23 of [Suppes] p. 97.
(ABA ≺ ℘A)
 
Theoremxpen 3383 Equinumerosity law for cross product. Proposition 4.22(b) of [Mendelson] p. 254.
AV    &   BV    &   CV    &   DV    ⇒   ((ABCD) → (A × C) ≈ (B × D))
 
Theoremmapenlem1 3384 Lemma for mapen 3386.
AV    &   BV    &   CV    &   DV    &   H = {⟨x, y⟩∣(x ∈ (Am C) ∧ y = ((fx) ∘ g))}    ⇒   ((((f:A1-1-ontoBg:C1-1-ontoD) ∧ z:C–→A) ∧ vC) → ((Hz) ‘(gv)) = (f ‘(zv)))
 
Theoremmapenlem2 3385 Lemma for mapen 3386.
AV    &   BV    &   CV    &   DV    &   H = {⟨x, y⟩∣(x ∈ (Am C) ∧ y = ((fx) ∘ g))}    ⇒   ((f:A1-1-ontoBg:C1-1-ontoD) → H:(Am C)–1-1-onto→(Bm D))
 
Theoremmapen 3386 Two set exponentiations are equinumerous when their bases and exponents are equinumerous. Theorem 6H(c) of [Enderton] p. 139.
AV    &   BV    &   CV    &   DV    ⇒   ((ABCD) → (Am C) ≈ (Bm D))
 
Theoremmapdom1 3387 Order-preserving property of set exponentiation. Theorem 6L(c) of [Enderton] p. 149.
AV    &   BV    &   CV    ⇒   (AB → (Am C) ≼ (Bm C))
 
Theoremmapdom2lem 3388 Lemma for mapdom2 3389.
AV    &   BV    &   CV    ⇒   (x ∈ (Cm z) → (x ∩ ((Bz) × {w})) = ∅)
 
Theoremmapdom2 3389 Order-preserving property of set exponentiation. Theorem 6L(d) of [Enderton] p. 149.
AV    &   BV    &   CV    ⇒   ((AB ∧ ¬ (A = ∅ ∧ C = ∅)) → (Cm A) ≼ (Cm B))
 
Theoremmapxpen 3390 Equinumerosity law for double set exponentiation. Proposition 10.45 of [TakeutiZaring] p. 96.
AV    &   BV    &   CV    ⇒   ((Am B) ↑m C) ≈ (Am (B × C))
 
Theoremxpmapenlem1 3391 Lemma for xpmapen 3396.
AV    &   BV    &   CV    &   D = {⟨z, w⟩∣(zCw = dom {(xz)})}    &   R = {⟨z, w⟩∣(zCw = ran {(xz)})}    &   S = {⟨z, w⟩∣(zCw = ⟨(dom {y} ‘z), (ran {y} ‘z)⟩)}    ⇒   ((y = ⟨D, R⟩ → ∀z y = ⟨D, R⟩) ∧ (y = ⟨D, R⟩ → ∀w y = ⟨D, R⟩))
 
Theoremxpmapenlem2 3392 Lemma for xpmapen 3396.
AV    &   BV    &   CV    &   D = {⟨z, w⟩∣(zCw = dom {(xz)})}    &   R = {⟨z, w⟩∣(zCw = ran {(xz)})}    &   S = {⟨z, w⟩∣(zCw = ⟨(dom {y} ‘z), (ran {y} ‘z)⟩)}    ⇒   ((y = ⟨D, R⟩ ∧ zC) → ((dom {y} ‘z) = dom {(xz)} ∧ (ran {y} ‘z) = ran {(xz)}))
 
Theoremxpmapenlem3 3393 Lemma for xpmapen 3396.
AV    &   BV    &   CV    &   D = {⟨z, w⟩∣(zCw = dom {(xz)})}    &   R = {⟨z, w⟩∣(zCw = ran {(xz)})}    &   S = {⟨z, w⟩∣(zCw = ⟨(dom {y} ‘z), (ran {y} ‘z)⟩)}    ⇒   ((x:C–→(A × B) ∧ y = ⟨D, R⟩) → x = S)
 
Theoremxpmapenlem4 3394 Lemma for xpmapen 3396.
AV    &   BV    &   CV    &   D = {⟨z, w⟩∣(zCw = dom {(xz)})}    &   R = {⟨z, w⟩∣(zCw = ran {(xz)})}    &   S = {⟨z, w⟩∣(zCw = ⟨(dom {y} ‘z), (ran {y} ‘z)⟩)}    ⇒   (((y = ⟨dom {y}, ran {y}⟩ ∧ (dom {y}:C–→Aran {y}:C–→B)) ∧ x = S) → (x:C–→(A × B) ∧ y = ⟨D, R⟩))
 
Theoremxpmapenlem5 3395 Lemma for xpmapen 3396.
AV    &   BV    &   CV    &   D = {⟨z, w⟩∣(zCw = dom {(xz)})}    &   R = {⟨z, w⟩∣(zCw = ran {(xz)})}    &   S = {⟨z, w⟩∣(zCw = ⟨(dom {y} ‘z), (ran {y} ‘z)⟩)}    ⇒   ((A × B) ↑m C) ≈ ((Am C) × (Bm C))
 
Theoremxpmapen 3396 Equinumerosity law for set exponentiation of a cross product. Exercise 4.47 of [Mendelson] p. 255.
AV    &   BV    &   CV    ⇒   ((A × B) ↑m C) ≈ ((Am C) × (Bm C))
 
Theoremmapunen 3397 Equinumerosity law for set exponentiation of a disjoint union. Exercise 4.45 of [Mendelson] p. 255.
AV    &   BV    &   CV    ⇒   ((AB) = ∅ → (Cm (AB)) ≈ ((Cm A) × (Cm B)))
 
Theorempwen 3398 If two sets are equinumerous, then their power sets are equinumerous. Proposition 10.15 of [TakeutiZaring] p. 87.
AV    &   BV    ⇒   (AB → ℘A ≈ ℘B)
 
Theoremssenen 3399 Equinumerosity of equinumerous subsets of a set.
AV    &   BV    &   CV    ⇒   (AB → {x∣(xAxC)} ≈ {x∣(xBxC)})
 
Theoremlimenpsi 3400 A limit ordinal is equinumerous to a proper subset of itself.
Lim A    ⇒   (ABA ≈ (A ∖ {∅}))

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