Theorem cbvabd | index | src |

theorem cbvabd {x y: nat} (G: wff) (p: wff x) (q: wff y):
  $ G /\ x = y -> (p <-> q) $ >
  $ G -> {x | p} == {y | q} $;
StepHypRefExpression
1 cbvabs
{x | p} == {y | [y / x] p}
2 1 a1i
G -> {x | p} == {y | [y / x] p}
3 sbet
A. x (x = y -> (p <-> q)) -> ([y / x] p <-> q)
4 hyp h
G /\ x = y -> (p <-> q)
5 4 ialda
G -> A. x (x = y -> (p <-> q))
6 3, 5 syl
G -> ([y / x] p <-> q)
7 6 abeqd
G -> {y | [y / x] p} == {y | q}
8 2, 7 eqstrd
G -> {x | p} == {y | q}

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)