Theorem d1lt2 ≪ | index | src | ≫ 

theorem d1lt2: $ 1 < 2 $;
StepHypRefExpression
1 ltsuc 
0 < 1 <-> suc 0 < suc 1
2 1 conv d1, d2 
0 < 1 <-> 1 < 2
3 d0lt1 
0 < 1
4 2, 3 mpbi 
1 < 2

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_peano (peano1, peano2, peano5, addeq, add0, addS)