Description: The union of a class is untangled iff all its members are untangled. (Contributed by Scott Fenton, 28-Feb-2011)
Ref | Expression | ||
---|---|---|---|
Assertion | untuni | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | r19.23v | |
|
2 | 1 | albii | |
3 | ralcom4 | |
|
4 | eluni2 | |
|
5 | 4 | imbi1i | |
6 | 5 | albii | |
7 | 2 3 6 | 3bitr4ri | |
8 | df-ral | |
|
9 | df-ral | |
|
10 | 9 | ralbii | |
11 | 7 8 10 | 3bitr4i | |