Description: 7 times 7 equals 49. (Contributed by Mario Carneiro, 19-Apr-2015)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | 7t7e49 | |- ( 7 x. 7 ) = ; 4 9 |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | 7nn0 | |- 7 e. NN0 |
|
| 2 | 6nn0 | |- 6 e. NN0 |
|
| 3 | df-7 | |- 7 = ( 6 + 1 ) |
|
| 4 | 7t6e42 | |- ( 7 x. 6 ) = ; 4 2 |
|
| 5 | 4nn0 | |- 4 e. NN0 |
|
| 6 | 2nn0 | |- 2 e. NN0 |
|
| 7 | eqid | |- ; 4 2 = ; 4 2 |
|
| 8 | 7cn | |- 7 e. CC |
|
| 9 | 2cn | |- 2 e. CC |
|
| 10 | 7p2e9 | |- ( 7 + 2 ) = 9 |
|
| 11 | 8 9 10 | addcomli | |- ( 2 + 7 ) = 9 |
| 12 | 5 6 1 7 11 | decaddi | |- ( ; 4 2 + 7 ) = ; 4 9 |
| 13 | 1 2 3 4 12 | 4t3lem | |- ( 7 x. 7 ) = ; 4 9 |