HomeHome Metamath Proof Explorer < Previous   Next >
Related theorems
Unicode version

Theorem pm4.81 358
Description: Theorem *4.81 of [WhiteheadRussell] p. 122.
Assertion
Ref Expression
pm4.81 |- ((-. ph -> ph) <-> ph)

Proof of Theorem pm4.81
StepHypRef Expression
1 pm2.18 100 . 2 |- ((-. ph -> ph) -> ph)
2 pm2.24 99 . 2 |- (ph -> (-. ph -> ph))
31, 2impbii 178 1 |- ((-. ph -> ph) <-> ph)
Colors of variables: wff set class
Syntax hints:  -. wn 3   -> wi 4   <-> wb 174
This theorem was proved from axioms:  ax-1 5  ax-2 6  ax-3 7  ax-mp 8
This theorem depends on definitions:  df-bi 175
Copyright terms: Public domain