Theorem nat0 ≪ | index | src | ≫ 

theorem nat0: $ nat F. = 0 $;
StepHypRefExpression
1 nateq0 
nat F. = 0 <-> ~F.
2 notfal 
~F.
3 1, 2 mpbir 
nat F. = 0

Axiom use

axs_prop_calc (ax_1, ax_2, ax_3, ax_mp, itru), axs_pred_calc (ax_gen, ax_4, ax_5, ax_6, ax_7, ax_10, ax_11, ax_12), axs_set (elab, ax_8), axs_the (theid), axs_peano (peano1)