Theorem true0 ≪ | index | src | ≫ 

theorem true0: $ ~true 0 $;
StepHypRefExpression
1 notnot1 
0 = 0 -> ~~0 = 0
2 1 conv ne, true 
0 = 0 -> ~true 0
3 eqid 
0 = 0
4 2, 3 ax_mp 
~true 0

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)