Metamath Proof Explorer


Theorem exp4c

Description: An exportation inference. (Contributed by NM, 26-Apr-1994)

Ref Expression
Hypothesis exp4c.1 φψχθτ
Assertion exp4c φψχθτ

Proof

Step Hyp Ref Expression
1 exp4c.1 φψχθτ
2 1 expd φψχθτ
3 2 expd φψχθτ