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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 3984 | . . 3 ⊢ (𝐹 = 𝐺 → (𝐴𝐹𝑥 ↔ 𝐴𝐺𝑥)) | |
2 | 1 | iotabidv 5174 | . 2 ⊢ (𝐹 = 𝐺 → (℩𝑥𝐴𝐹𝑥) = (℩𝑥𝐴𝐺𝑥)) |
3 | df-fv 5196 | . 2 ⊢ (𝐹‘𝐴) = (℩𝑥𝐴𝐹𝑥) | |
4 | df-fv 5196 | . 2 ⊢ (𝐺‘𝐴) = (℩𝑥𝐴𝐺𝑥) | |
5 | 2, 3, 4 | 3eqtr4g 2224 | 1 ⊢ (𝐹 = 𝐺 → (𝐹‘𝐴) = (𝐺‘𝐴)) |
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