Description: A special case of ax-c5 without using ax-c5 or ax-5 . (Contributed by NM, 13-Jan-2011) (Proof modification is discouraged.) (New usage is discouraged.)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | axc5sp1 | |- ( A. y -. x = x -> -. x = x ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | equidqe | |- -. A. y -. x = x |
|
| 2 | 1 | pm2.21i | |- ( A. y -. x = x -> -. x = x ) |