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Theorem eupick 2632
Description: Existential uniqueness "picks" a variable value for which another wff is true. If there is only one thing 𝑥 such that 𝜑 is true, and there is also an 𝑥 (actually the same one) such that 𝜑 and 𝜓 are both true, then 𝜑 implies 𝜓 regardless of 𝑥. This theorem can be useful for eliminating existential quantifiers in a hypothesis. Compare Theorem *14.26 in [WhiteheadRussell] p. 192. (Contributed by NM, 10-Jul-1994.)
Assertion
Ref Expression
eupick ((∃!𝑥𝜑 ∧ ∃𝑥(𝜑𝜓)) → (𝜑𝜓))

Proof of Theorem eupick
StepHypRef Expression
1 eumo 2577 . 2 (∃!𝑥𝜑 → ∃*𝑥𝜑)
2 mopick 2624 . 2 ((∃*𝑥𝜑 ∧ ∃𝑥(𝜑𝜓)) → (𝜑𝜓))
31, 2sylan 580 1 ((∃!𝑥𝜑 ∧ ∃𝑥(𝜑𝜓)) → (𝜑𝜓))
Colors of variables: wff setvar class
Syntax hints:  wi 4  wa 395  wex 1778  ∃*wmo 2537  ∃!weu 2567
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1794  ax-4 1808  ax-5 1909  ax-6 1966  ax-7 2006  ax-12 2176
This theorem depends on definitions:  df-bi 207  df-an 396  df-ex 1779  df-mo 2539  df-eu 2568
This theorem is referenced by:  eupicka  2633  eupickb  2634  reupick  4328  reupick3  4329  eusv2nf  5394  reusv2lem3  5399  copsexgw  5494  copsexg  5495  funssres  6609  oprabidw  7463  oprabid  7464  txcn  23635  isch3  31261  bnj849  34940  iotasbc  44443
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