Theorem preldm | index | src |

theorem preldm (A: set) (a b: nat): $ a, b e. A -> a e. Dom A $;
StepHypRefExpression
1 eldm
a e. Dom A <-> E. y a, y e. A
2 preq2
y = b -> a, y = a, b
3 2 eleq1d
y = b -> (a, y e. A <-> a, b e. A)
4 3 iexe
a, b e. A -> E. y a, y e. A
5 1, 4 sylibr
a, b e. A -> a e. Dom A

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), axs_the (theid, the0), axs_peano (peano2, addeq, muleq)