Metamath Proof Explorer

Theorem efald2

Description: A proof by contradiction. (Contributed by Giovanni Mascellani, 15-Sep-2017)

Ref Expression
Hypothesis efald2.1 
|- ( -. ph -> F. )
Assertion efald2 
|- ph

Proof

Step Hyp Ref Expression
1 efald2.1 
 |-  ( -. ph -> F. )
2 1 adantl 
 |-  ( ( T. /\ -. ph ) -> F. )
3 2 efald 
 |-  ( T. -> ph )
4 3 mptru 
 |-  ph