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| Mirrors > Home > ILE Home > Th. List > fveq1 | GIF version | ||
| Description: Equality theorem for function value. (Contributed by NM, 29-Dec-1996.) | 
| Ref | Expression | 
|---|---|
| fveq1 | ⊢ (𝐹 = 𝐺 → (𝐹‘𝐴) = (𝐺‘𝐴)) | 
| Step | Hyp | Ref | Expression | 
|---|---|---|---|
| 1 | breq 4035 | . . 3 ⊢ (𝐹 = 𝐺 → (𝐴𝐹𝑥 ↔ 𝐴𝐺𝑥)) | |
| 2 | 1 | iotabidv 5241 | . 2 ⊢ (𝐹 = 𝐺 → (℩𝑥𝐴𝐹𝑥) = (℩𝑥𝐴𝐺𝑥)) | 
| 3 | df-fv 5266 | . 2 ⊢ (𝐹‘𝐴) = (℩𝑥𝐴𝐹𝑥) | |
| 4 | df-fv 5266 | . 2 ⊢ (𝐺‘𝐴) = (℩𝑥𝐴𝐺𝑥) | |
| 5 | 2, 3, 4 | 3eqtr4g 2254 | 1 ⊢ (𝐹 = 𝐺 → (𝐹‘𝐴) = (𝐺‘𝐴)) | 
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