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Metamath Proof Explorer
Description: Axiom *1.6 (Sum) of WhiteheadRussell p. 97. (Contributed by NM, 3-Jan-2005)
|
|
Ref |
Expression |
|
Assertion |
orim2 |
⊢ ( ( 𝜓 → 𝜒 ) → ( ( 𝜑 ∨ 𝜓 ) → ( 𝜑 ∨ 𝜒 ) ) ) |
Proof
| Step |
Hyp |
Ref |
Expression |
| 1 |
|
id |
⊢ ( ( 𝜓 → 𝜒 ) → ( 𝜓 → 𝜒 ) ) |
| 2 |
1
|
orim2d |
⊢ ( ( 𝜓 → 𝜒 ) → ( ( 𝜑 ∨ 𝜓 ) → ( 𝜑 ∨ 𝜒 ) ) ) |