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Statement List for Metamath Proof Explorer - 1301-1400 - Page 14 of 105
TypeLabelDescription
Statement
 
Theoremcbvex2v 1301 Rule used to change bound variables with implicit substitution.
|- ((x = z /\ y = w) -> (ph <-> ps))   =>   |- (E.xE.yph <-> E.zE.wps)
 
Theoremcbvald 1302 Deduction used to change bound variables with implicit substitution, particularly useful in conjunction with dvelim 1334.
|- (ph -> A.yph)   &   |- (ph -> (ps -> A.yps))   &   |- (ph -> (x = y -> (ps <-> ch)))   =>   |- (ph -> (A.xps <-> A.ych))
 
Theoremcbvexd 1303 Deduction used to change bound variables with implicit substitution, particularly useful in conjunction with dvelim 1334.
|- (ph -> A.yph)   &   |- (ph -> (ps -> A.yps))   &   |- (ph -> (x = y -> (ps <-> ch)))   =>   |- (ph -> (E.xps <-> E.ych))
 
Theoremcbvex4v 1304 Rule used to change bound variables with implicit substitution.
|- ((x = v /\ y = u) -> (ph <-> ps))   &   |- ((z = f /\ w = g) -> (ps <-> ch))   =>   |- (E.xE.yE.zE.wph <-> E.vE.uE.fE.gch)
 
Theoremeeanv 1305 Rearrange existential quantifiers.
|- (E.xE.y(ph /\ ps) <-> (E.xph /\ E.yps))
 
Theoremeeeanv 1306 Rearrange existential quantifiers.
|- (E.xE.yE.z(ph /\ ps /\ ch) <-> (E.xph /\ E.yps /\ E.zch))
 
Theoremee4anv 1307 Rearrange existential quantifiers.
|- (E.xE.yE.zE.w(ph /\ ps) <-> (E.xE.yph /\ E.zE.wps))
 
Theoremnexdv 1308 Deduction for generalization rule for negated wff.
|- (ph -> -. ps)   =>   |- (ph -> -. E.xps)
 
Theoremchvarv 1309 Implicit substitution of y for x into a theorem.
|- (x = y -> (ph <-> ps))   &   |- ph   =>   |- ps
 
Theoremcleljust 1310 When the class variables in definition df-clel 1449 are replaced with set variables, this theorem of predicate calculus is the result. This theorem provides part of the justification for the consistency of that definition, which "overloads" the set variables in wel 1106 with the class variables in wcel 1105.
|- (x e. y <-> E.z(z = x /\ z e. y))
 
More substitution theorems
 
Theoremequsb3lem 1311 Lemma for equsb3 1312.
 
Theoremequsb3 1312 Substitution applied to an atomic wff. (Contributed by Raph Levien and FL, 4-Dec-2005.)
|- ([x / y]y = z <-> x = z)
 
Theoremelsb3 1313 Substitution applied to an atomic membership wff.
|- ([x / y]y e. z <-> x e. z)
 
Theoremhbs1 1314 x is not free in [y / x]ph when x and y are distinct.
|- ([y / x]ph -> A.x[y / x]ph)
 
Theoremhbsb 1315 If z is not free in ph, it is not free in [y / x]ph when y and z are distinct.
|- (ph -> A.zph)   =>   |- ([y / x]ph -> A.z[y / x]ph)
 
Theoremsbcom2 1316 Commutativity law for substitution. Used in proof of Theorem 9.7 of [Megill] p. 449 (p. 16 of the preprint).
|- ([w / z][y / x]ph <-> [y / x][w / z]ph)
 
Theorem2sb5 1317 Equivalence for double substitution.
|- ([z / x][w / y]ph <-> E.xE.y((x = z /\ y = w) /\ ph))
 
Theorem2sb6 1318 Equivalence for double substitution.
|- ([z / x][w / y]ph <-> A.xA.y((x = z /\ y = w) -> ph))
 
Theoremsb6a 1319 Equivalence for substitution.
|- ([y / x]ph <-> A.x(x = y -> [x / y]ph))
 
Theorem2sb5rf 1320 Reversed double substitution.
|- (ph -> A.zph)   &   |- (ph -> A.wph)   =>   |- (ph <-> E.zE.w((z = x /\ w = y) /\ [z / x][w / y]ph))
 
Theorem2sb6rf 1321 Reversed double substitution.
|- (ph -> A.zph)   &   |- (ph -> A.wph)   =>   |- (ph <-> A.zA.w((z = x /\ w = y) -> [z / x][w / y]ph))
 
Theoremsb7 1322 An alternate definition of proper substitution df-sb 1155. By introducing a dummy variable z in the definiens, we are able to eliminate any distinct variable restrictions among the variables x, y, and ph of the definiendum. No distinct variable conflicts arise because z effectively insulates x from y. To achieve this, we use a chain of two substitutions in the form of sb5 1252, first z for x then y for z. Compare Definition 2.1'' of [Quine] p. 17, which is obtained from this theorem by applying df-clab 1441. Theorem sb7f 1323 provides a version where ph and z don't have to be distinct.
|- ([y / x]ph <-> E.z(z = y /\ E.x(x = z /\ ph)))
 
Theoremsb7f 1323 This version of sb7 1322 does not require that ph and z be distinct. This permits it to be used as a definition for substitution in a formalization that omits the logically redundant axiom ax-17 1190 i.e. that doesn't have the concept of a variable not occurring in a wff. (df-sb 1155 is also suitable, but its mixing of free and bound variables is distasteful to some logicians.)
|- (ph -> A.zph)   =>   |- ([y / x]ph <-> E.z(z = y /\ E.x(x = z /\ ph)))
 
Theoremsb10f 1324 Hao Wang's identity axiom P6 in Irving Copi, Symbolic Logic (5th ed., 1979), p. 328. In traditional predicate calculus, this is a sole axiom for identity from which the usual ones can be derived.
|- (ph -> A.xph)   =>   |- ([y / z]ph <-> E.x(x = y /\ [x / z]ph))
 
Theoremsbid2v 1325 An identity law for substitution. Used in proof of Theorem 9.7 of [Megill] p. 449 (p. 16 of the preprint).
|- ([y / x][x / y]ph <-> ph)
 
Theoremsbelx 1326 Elimination of substitution.
|- (ph <-> E.x(x = y /\ [x / y]ph))
 
Theoremsbel2x 1327 Elimination of double substitution.
|- (ph <-> E.xE.y((x = z /\ y = w) /\ [y / w][x / z]ph))
 
Theoremsbal1 1328 A theorem used in elimination of disjoint variable restriction on x and y by replacing it with a distinctor -. A.xx = z.
|- (-. A.x x = z -> ([z / y]A.xph <-> A.x[z / y]ph))
 
Theoremsbal 1329 Move universal quantifier in and out of substitution.
|- ([z / y]A.xph <-> A.x[z / y]ph)
 
Theoremsbex 1330 Move existential quantifier in and out of substitution.
|- ([z / y]E.xph <-> E.x[z / y]ph)
 
Theoremsbalv 1331 Quantify with new variable inside substitution.
|- ([y / x]ph <-> ps)   =>   |- ([y / x]A.zph <-> A.zps)
 
Theoremexsb 1332 An equivalent expression for existence.
|- (E.xph <-> E.yA.x(x = y -> ph))
 
Theorem2exsb 1333 An equivalent expression for double existence.
|- (E.xE.yph <-> E.zE.wA.xA.y((x = z /\ y = w) -> ph))
 
Theoremdvelim 1334 This theorem can be used to eliminate a distinct variable restriction on x and z and replace it with the "distinctor" -. A.xx = y as an antecedent. ph is considered to contain z, and ps to have z replaced with y, and we don't require that x and y be distinct (if they aren't, the distinctor will become false and "protect" the consequent).

To obtain a closed theorem form of this inference, conjoin the hypotheses and apply dvelimdf 1235.

|- (ph -> A.xph)   &   |- (z = y -> (ph <-> ps))   =>   |- (-. A.x x = y -> (ps -> A.xps))
 
Theoremdveeq1 1335 Quantifier introduction when one pair of variables is distinct.
|- (-. A.x x = y -> (y = z -> A.x y = z))
 
Theoremdveel1 1336 Quantifier introduction when one pair of variables is distinct.
|- (-. A.x x = y -> (y e. z -> A.x y e. z))
 
Theoremdveel2 1337 Quantifier introduction when one pair of variables is distinct.
|- (-. A.x x = y -> (z e. y -> A.x z e. y))
 
Theoremsbal2 1338 Move quantifier in and out of substitution.
|- (-. A.x x = y -> ([z / y]A.xph <-> A.x[z / y]ph))
 
Theoremax15 1339 Axiom ax-15 1109 is redundant if we assume ax-17 1190. Remark 9.6 in [Megill] p. 448 (p. 16 of the preprint), regarding axiom scheme C14'.

Note that w is a dummy variable introduced in the proof. On the web page, it is implicitly assumed to be distinct from all other variables. (This is made explicit in the database file set.mm). Its purpose is to satisfy the distinct variable requirements of dveel2 1337 and dvelim 1334. By the end of the proof it has vanished, and the final theorem has no distinct variable requirements.

|- (-. A.z z = x -> (-. A.z z = y -> (x e. y -> A.z x e. y)))
 
Theoremax11eq 1340 Basis step for constructing a substitution instance of ax-11o 1202 without using ax-11o 1202. Atomic formula for equality predicate.
|- (-. A.x x = y -> (x = y -> (z = w -> A.x(x = y -> z = w))))
 
Theoremax11el 1341 Basis step for constructing a substitution instance of ax-11o 1202 without using ax-11o 1202. Atomic formula for membership predicate.
|- (-. A.x x = y -> (x = y -> (z e. w -> A.x(x = y -> z e. w))))
 
Theoremax11f 1342 Basis step for constructing a substitution instance of ax-11o 1202 without using ax-11o 1202. We can start with any formula ph in which x is not free.
|- (ph -> A.xph)   =>   |- (-. A.x x = y -> (x = y -> (ph -> A.x(x = y -> ph))))
 
Theoremax11indn 1343 Induction step for constructing a substitution instance of ax-11o 1202 without using ax-11o 1202. Negation case.
|- (-. A.x x = y -> (x = y -> (ph -> A.x(x = y -> ph))))   =>   |- (-. A.x x = y -> (x = y -> (-. ph -> A.x(x = y -> -. ph))))
 
Theoremax11indi 1344 Induction step for constructing a substitution instance of ax-11o 1202 without using ax-11o 1202. Implication case.
|- (-. A.x x = y -> (x = y -> (ph -> A.x(x = y -> ph))))   &   |- (-. A.x x = y -> (x = y -> (ps -> A.x(x = y -> ps))))   =>   |- (-. A.x x = y -> (x = y -> ((ph -> ps) -> A.x(x = y -> (ph -> ps)))))
 
Theoremax11indalem 1345 Lemma for ax11inda2 1347 and ax11inda 1348.
 
Theoremax11inda2ALT 1346 A proof of ax11inda2 1347 that is slightly more direct.
|- (-. A.x x = y -> (x = y -> (ph -> A.x(x = y -> ph))))   =>   |- (-. A.x x = y -> (x = y -> (A.zph -> A.x(x = y -> A.zph))))
 
Theoremax11inda2 1347 Induction step for constructing a substitution instance of ax-11o 1202 without using ax-11o 1202. Quantification case. When z and y are distinct, this theorem avoids the dummy variables needed by the more general ax11inda 1348.
|- (-. A.x x = y -> (x = y -> (ph -> A.x(x = y -> ph))))   =>   |- (-. A.x x = y -> (x = y -> (A.zph -> A.x(x = y -> A.zph))))
 
Theoremax11inda 1348 Induction step for constructing a substitution instance of ax-11o 1202 without using ax-11o 1202. Quantification case. (When z and y are distinct, ax11inda2 1347 may be used instead to avoid the dummy variable w in the proof.)