Description: -u 1 x. -u 1 is 1. (Contributed by David A. Wheeler, 8-Dec-2018)
Ref | Expression | ||
---|---|---|---|
Assertion | neg1mulneg1e1 | ⊢ ( - 1 · - 1 ) = 1 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | ax-1cn | ⊢ 1 ∈ ℂ | |
2 | 1 1 | mul2negi | ⊢ ( - 1 · - 1 ) = ( 1 · 1 ) |
3 | 1t1e1 | ⊢ ( 1 · 1 ) = 1 | |
4 | 2 3 | eqtri | ⊢ ( - 1 · - 1 ) = 1 |