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Mirrors > Home > ILE Home > Th. List > notbid | GIF version |
Description: Equivalence property for negation. Deduction form. (Contributed by NM, 21-May-1994.) (Revised by Mario Carneiro, 31-Jan-2015.) |
Ref | Expression |
---|---|
notbid.1 | ⊢ (𝜑 → (𝜓 ↔ 𝜒)) |
Ref | Expression |
---|---|
notbid | ⊢ (𝜑 → (¬ 𝜓 ↔ ¬ 𝜒)) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | notbid.1 | . 2 ⊢ (𝜑 → (𝜓 ↔ 𝜒)) | |
2 | notbi 656 | . 2 ⊢ ((𝜓 ↔ 𝜒) → (¬ 𝜓 ↔ ¬ 𝜒)) | |
3 | 1, 2 | syl 14 | 1 ⊢ (𝜑 → (¬ 𝜓 ↔ ¬ 𝜒)) |
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