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Metamath Proof Explorer

Theorem tb-ax1

Description: The first of three axioms in the Tarski-Bernays axiom system. (Contributed by Anthony Hart, 16-Aug-2011) (Proof modification is discouraged.) (New usage is discouraged.)

Ref Expression
Assertion tb-ax1 
|- ( ( ph -> ps ) -> ( ( ps -> ch ) -> ( ph -> ch ) ) )

Proof

Step Hyp Ref Expression
1 imim1 
 |-  ( ( ph -> ps ) -> ( ( ps -> ch ) -> ( ph -> ch ) ) )