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Description: Deduction converting an implication to a biconditional with conjunction. Deduction from Theorem *4.71 of WhiteheadRussell p. 120. (Contributed by Mario Carneiro, 25-Dec-2016)
| Ref | Expression | ||
|---|---|---|---|
| Hypothesis | pm4.71rd.1 | ⊢ ( 𝜑 → ( 𝜓 → 𝜒 ) ) | |
| Assertion | pm4.71d | ⊢ ( 𝜑 → ( 𝜓 ↔ ( 𝜓 ∧ 𝜒 ) ) ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | pm4.71rd.1 | ⊢ ( 𝜑 → ( 𝜓 → 𝜒 ) ) | |
| 2 | pm4.71 | ⊢ ( ( 𝜓 → 𝜒 ) ↔ ( 𝜓 ↔ ( 𝜓 ∧ 𝜒 ) ) ) | |
| 3 | 1 2 | sylib | ⊢ ( 𝜑 → ( 𝜓 ↔ ( 𝜓 ∧ 𝜒 ) ) ) |