Description: The following User's Proof is a Natural Deduction Sequent Calculus
transcription of the Fitchstyle Natural Deduction proof of Theorem 7 of
Section 14 of [Margaris] p. 60 ( which is con3 126). The same proof
may also be interpreted to be a Virtual Deduction Hilbertstyle
axiomatic proof. It was completed automatically by the tools program
completeusersproof.cmd, which invokes Mel O'Cat's mmj2 and Norm Megill's
Metamath Proof Assistant. con3ALT 28592 is con3ALTVD 29008
without virtual deductions and was automatically derived
from con3ALTVD 29008. Step i of the User's Proof corresponds to
step i of the Fitchstyle proof.
1:: 
 2:: 
 3:: 
 4:2: 
 5:1,4: 
 6:: 
 7:6,5: 
 8:7: 
 9:: 
 10:8: 
 qed:10: 

(Contributed by Alan Sare, 21Apr2013.) (Proof modification is
discouraged.) (New usage is discouraged.) 