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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 667 | . 2 ⊢ ((𝜓 ↔ 𝜒) → (¬ 𝜓 ↔ ¬ 𝜒)) | |
| 3 | 1, 2 | syl 14 | 1 ⊢ (𝜑 → (¬ 𝜓 ↔ ¬ 𝜒)) |
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