Description: An opposite category is a category. (Contributed by Mario Carneiro, 2-Jan-2017)
Ref | Expression | ||
---|---|---|---|
Hypothesis | oppcbas.1 | |
|
Assertion | oppccat | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | oppcbas.1 | |
|
2 | 1 | oppccatid | |
3 | 2 | simpld | |