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| Mirrors > Home > MPE Home > Th. List > sseq1 | Structured version Visualization version Unicode version | ||
| Description: Equality theorem for subclasses. (Contributed by NM, 24-Jun-1993.) (Proof shortened by Andrew Salmon, 21-Jun-2011.) |
| Ref | Expression |
|---|---|
| sseq1 |
|
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | eqss 3618 |
. 2
| |
| 2 | sstr2 3610 |
. . . 4
| |
| 3 | 2 | adantl 482 |
. . 3
|
| 4 | sstr2 3610 |
. . . 4
| |
| 5 | 4 | adantr 481 |
. . 3
|
| 6 | 3, 5 | impbid 202 |
. 2
|
| 7 | 1, 6 | sylbi 207 |
1
|
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