Theorem true_iff_true_iff_true ≪ | index | src | ≫

\iff真值表：(\true \iff \true) \iff \true

theorem true_iff_true_iff_true: $ (\true \iff \true) \iff \true $;

Step	Hyp	Ref	Expression
1		prov_iff_true	(\true \iff \true) \imp ((\true \iff \true) \iff \true)
2		iff_refl	\true \iff \true
3	1, 2	ax_mp	(\true \iff \true) \iff \true

Axiom use

Logic (ax_mp, ax_1, ax_2, ax_3)