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Description: Utility theorem: index-independent form of df-ds . (Contributed by Mario Carneiro, 23-Dec-2013)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | dsid |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | df-ds | ||
| 2 | 1nn0 | ||
| 3 | 2nn | ||
| 4 | 2 3 | decnncl | |
| 5 | 1 4 | ndxid |