Theorem pm2.21fal 1384

Description: If a wff and its negation are provable, then falsum is provable. (Contributed by Mario Carneiro, 9-Feb-2017.)

Hypotheses

Ref	Expression
pm2.21fal.1	|- ( ph -> ps )
pm2.21fal.2	|- ( ph -> -. ps )

Assertion

Ref	Expression
pm2.21fal	|- ( ph -> F. )

Proof of Theorem pm2.21fal

Step	Hyp	Ref	Expression
1		pm2.21fal.1	. 2 |- ( ph -> ps )
2		pm2.21fal.2	. 2 |- ( ph -> -. ps )
3	1, 2	pm2.21dd 621	1 |- ( ph -> F. )

Syntax hints:   -. wn 3   -> wi 4   F. wfal 1369

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-in2 616

This theorem is referenced by:  genpdisj  7609  suplocexprlemdisj  7806  suplocexprlemub  7809  suplocsrlem  7894  recvguniqlem  11178  resqrexlemoverl  11205  leabs  11258  climge0  11509  isprm5lem  12336  dedekindeulemeu  14966  dedekindicclemeu  14975  pw1nct  15758