Description: Special case of closed form of a2d . Special case of rp-frege4g . Proposition 4 of Frege1879 p. 31. (Contributed by RP, 24-Dec-2019) (Proof modification is discouraged.)
Ref | Expression | ||
---|---|---|---|
Assertion | frege4 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | frege3 | ||
2 | ax-frege2 | ||
3 | 1 2 | ax-mp |