Theorem nat1 ≪ | index | src | ≫ 

theorem nat1: $ nat T. = 1 $;
StepHypRefExpression
1 nateq1 
nat T. = 1 <-> T.
2 itru 
T.
3 1, 2 mpbir 
nat T. = 1

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, peano2, peano5, addeq, add0, addS)