Metamath Proof Explorer

Theorem atbiffatnnbalt

Description: If a implies b, then a implies not not b. (Contributed by Jarvin Udandy, 29-Aug-2016)

Ref Expression
Assertion atbiffatnnbalt 
|- ( ( ph -> ps ) -> ( ph -> -. -. ps ) )

Proof

Step Hyp Ref Expression
1 atbiffatnnb 
 |-  ( ( ph -> ps ) -> ( ph -> -. -. ps ) )