Description: Proposition 107 of Frege1879 p. 74. (Contributed by RP, 7-Jul-2020) (Proof modification is discouraged.)
Ref | Expression | ||
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Hypothesis | frege107.v | |- V e. A |
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Assertion | frege107 | |- ( ( Z ( ( t+ ` R ) u. _I ) Y -> ( Y R V -> Z ( t+ ` R ) V ) ) -> ( Z ( ( t+ ` R ) u. _I ) Y -> ( Y R V -> Z ( ( t+ ` R ) u. _I ) V ) ) ) |
Step | Hyp | Ref | Expression |
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1 | frege107.v | |- V e. A |
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2 | 1 | frege106 | |- ( Z ( t+ ` R ) V -> Z ( ( t+ ` R ) u. _I ) V ) |
3 | frege7 | |- ( ( Z ( t+ ` R ) V -> Z ( ( t+ ` R ) u. _I ) V ) -> ( ( Z ( ( t+ ` R ) u. _I ) Y -> ( Y R V -> Z ( t+ ` R ) V ) ) -> ( Z ( ( t+ ` R ) u. _I ) Y -> ( Y R V -> Z ( ( t+ ` R ) u. _I ) V ) ) ) ) |
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4 | 2 3 | ax-mp | |- ( ( Z ( ( t+ ` R ) u. _I ) Y -> ( Y R V -> Z ( t+ ` R ) V ) ) -> ( Z ( ( t+ ` R ) u. _I ) Y -> ( Y R V -> Z ( ( t+ ` R ) u. _I ) V ) ) ) |