Theorem Powereq ≪ | index | src | ≫ 

theorem Powereq (_A1 _A2: set): $ _A1 == _A2 -> Power _A1 == Power _A2 $;
StepHypRefExpression
1 id 
_A1 == _A2 -> _A1 == _A2
2 1 Powereqd 
_A1 == _A2 -> Power _A1 == Power _A2

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)