Theorem cbvabs | index | src |

theorem cbvabs {x y: nat} (p: wff x): $ {x | p} == {y | [y / x] p} $;
StepHypRefExpression
1 nfv
F/ y p
2 nfsb1
F/ x [y / x] p
3 sbq
x = y -> (p <-> [y / x] p)
4 1, 2, 3 cbvabh
{x | p} == {y | [y / x] p}

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)