Description: Contraposition law for polarity. Remark in Holland95 p. 223. (Contributed by NM, 23-Mar-2012) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Hypotheses | 2polss.a | |
|
2polss.p | |
||
Assertion | polcon3N | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 2polss.a | |
|
2 | 2polss.p | |
|
3 | simp3 | |
|
4 | iinss1 | |
|
5 | sslin | |
|
6 | 3 4 5 | 3syl | |
7 | eqid | |
|
8 | eqid | |
|
9 | 7 1 8 2 | polvalN | |
10 | 9 | 3adant3 | |
11 | simp1 | |
|
12 | simp2 | |
|
13 | 3 12 | sstrd | |
14 | 7 1 8 2 | polvalN | |
15 | 11 13 14 | syl2anc | |
16 | 6 10 15 | 3sstr4d | |