Theorem el3v

Description: New way ( elv , and the theorems beginning with "el2v" or "el3v") to shorten some proofs. Inference forms (with |- A e.V , |- B e. V and |- C e. _V hypotheses) of the general theorems (proving |- ( ( A e. V /\ B e. W /\ C e. X ) -> assertions) may be superfluous. (Contributed by Peter Mazsa, 13-Oct-2018)

	Ref	Expression
Hypothesis	el3v.1	|- ( ( x e. _V /\ y e. _V /\ z e. _V ) -> ph )
Assertion	el3v	|- ph

Proof

Step	Hyp	Ref	Expression
1		el3v.1	|- ( ( x e. _V /\ y e. _V /\ z e. _V ) -> ph )
2		vex	|- x e. _V
3		vex	|- y e. _V
4		vex	|- z e. _V
5	2 3 4 1	mp3an	|- ph