Description: The factorial of 4. (Contributed by Mario Carneiro, 18-Jun-2015)
Ref | Expression | ||
---|---|---|---|
Assertion | fac4 | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | 3nn0 | |
|
2 | facp1 | |
|
3 | 1 2 | ax-mp | |
4 | 3p1e4 | |
|
5 | 4 | fveq2i | |
6 | fac3 | |
|
7 | 6 4 | oveq12i | |
8 | 6t4e24 | |
|
9 | 7 8 | eqtri | |
10 | 3 5 9 | 3eqtr3i | |