Theorem com23 | index | src |

theorem com23 (a b c d: wff): $ a -> b -> c -> d $ > $ a -> c -> b -> d $;
StepHypRefExpression
1 mpcom
c -> (c -> d) -> d
2 1 imim2d
c -> (b -> c -> d) -> b -> d
3 2 com12
(b -> c -> d) -> c -> b -> d
4 hyp h
a -> b -> c -> d
5 3, 4 syl
a -> c -> b -> d

Axiom use

axs_prop_calc (ax_1, ax_2, ax_mp)