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| Mirrors > Home > ILE Home > Th. List > csbeq1a | GIF version | ||
| Description: Equality theorem for proper substitution into a class. (Contributed by NM, 10-Nov-2005.) | 
| Ref | Expression | 
|---|---|
| csbeq1a | ⊢ (𝑥 = 𝐴 → 𝐵 = ⦋𝐴 / 𝑥⦌𝐵) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | csbid 3092 | . 2 ⊢ ⦋𝑥 / 𝑥⦌𝐵 = 𝐵 | |
| 2 | csbeq1 3087 | . 2 ⊢ (𝑥 = 𝐴 → ⦋𝑥 / 𝑥⦌𝐵 = ⦋𝐴 / 𝑥⦌𝐵) | |
| 3 | 1, 2 | eqtr3id 2243 | 1 ⊢ (𝑥 = 𝐴 → 𝐵 = ⦋𝐴 / 𝑥⦌𝐵) | 
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