Description: Substitution of equal classes into membership relation. (Contributed by NM, 15-Jul-1993)
Ref | Expression | ||
---|---|---|---|
Hypotheses | eleqtri.1 | |
|
eleqtri.2 | |
||
Assertion | eleqtri | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eleqtri.1 | |
|
2 | eleqtri.2 | |
|
3 | 2 | eleq2i | |
4 | 1 3 | mpbi | |