Theorem Arroweq2 ≪ | index | src | ≫ 

theorem Arroweq2 (A _B1 _B2: set): $ _B1 == _B2 -> Arrow A _B1 == Arrow A _B2 $;
StepHypRefExpression
1 id 
_B1 == _B2 -> _B1 == _B2
2 1 Arroweq2d 
_B1 == _B2 -> Arrow A _B1 == Arrow A _B2

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)