Description: Set substitution into the first argument of a subset relation. (Contributed by Rodolfo Medina, 7-Jul-2010) (Proof shortened by Mario Carneiro, 14-Nov-2016)
Ref | Expression | ||
---|---|---|---|
Assertion | sbss | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | sseq1 | |
|
2 | sseq1 | |
|
3 | 1 2 | sbievw2 | |