Theorem
biid
≪
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index
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src
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≫
theorem biid (a: wff): $ a <-> a $;
Step
Hyp
Ref
Expression
1
id
a -> a
2
1
,
1
ibii
a <-> a
Axiom use
axs_prop_calc
(
ax_1
,
ax_2
,
ax_3
,
ax_mp
)