Theorem neeq2d ≪ | index | src | ≫ 

theorem neeq2d (_G: wff) (a _b1 _b2: nat):
  $ _G -> _b1 = _b2 $ >
  $ _G -> (a != _b1 <-> a != _b2) $;
StepHypRefExpression
1 eqidd 
_G -> a = a
2 hyp _h 
_G -> _b1 = _b2
3 1, 2 neeqd 
_G -> (a != _b1 <-> a != _b2)

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp), axs_pred_calc (ax_gen, ax_4, ax_5, ax_6, ax_7)