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Metamath Proof Explorer
Description: Theorem *2.31 of WhiteheadRussell p. 104. (Contributed by NM, 3-Jan-2005)
|
|
Ref |
Expression |
|
Assertion |
pm2.31 |
⊢ ( ( 𝜑 ∨ ( 𝜓 ∨ 𝜒 ) ) → ( ( 𝜑 ∨ 𝜓 ) ∨ 𝜒 ) ) |
Proof
| Step |
Hyp |
Ref |
Expression |
| 1 |
|
orass |
⊢ ( ( ( 𝜑 ∨ 𝜓 ) ∨ 𝜒 ) ↔ ( 𝜑 ∨ ( 𝜓 ∨ 𝜒 ) ) ) |
| 2 |
1
|
biimpri |
⊢ ( ( 𝜑 ∨ ( 𝜓 ∨ 𝜒 ) ) → ( ( 𝜑 ∨ 𝜓 ) ∨ 𝜒 ) ) |