Metamath Proof Explorer
Description: Theorem *13.18 in WhiteheadRussell p. 178. (Contributed by Andrew
Salmon, 3-Jun-2011) (Proof shortened by Wolf Lammen, 14-May-2023)
|
|
Ref |
Expression |
|
Assertion |
pm13.18 |
⊢ ( ( 𝐴 = 𝐵 ∧ 𝐴 ≠ 𝐶 ) → 𝐵 ≠ 𝐶 ) |
Proof
Step |
Hyp |
Ref |
Expression |
1 |
|
neeq1 |
⊢ ( 𝐴 = 𝐵 → ( 𝐴 ≠ 𝐶 ↔ 𝐵 ≠ 𝐶 ) ) |
2 |
1
|
biimpd |
⊢ ( 𝐴 = 𝐵 → ( 𝐴 ≠ 𝐶 → 𝐵 ≠ 𝐶 ) ) |
3 |
2
|
imp |
⊢ ( ( 𝐴 = 𝐵 ∧ 𝐴 ≠ 𝐶 ) → 𝐵 ≠ 𝐶 ) |