Theorem aneq ≪ | index | src | ≫ 

theorem aneq (a b c d: wff): $ (a <-> b) -> (c <-> d) -> (a /\ c <-> b /\ d) $;
StepHypRefExpression
1 anl 
(a <-> b) /\ (c <-> d) -> (a <-> b)
2 anr 
(a <-> b) /\ (c <-> d) -> (c <-> d)
3 1, 2 aneqd 
(a <-> b) /\ (c <-> d) -> (a /\ c <-> b /\ d)
4 3 exp 
(a <-> b) -> (c <-> d) -> (a /\ c <-> b /\ d)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp)