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Mirrors > Home > MPE Home > Th. List > sneq | Structured version Visualization version GIF version |
Description: Equality theorem for singletons. Part of Exercise 4 of [TakeutiZaring] p. 15. (Contributed by NM, 21-Jun-1993.) |
Ref | Expression |
---|---|
sneq | ⊢ (𝐴 = 𝐵 → {𝐴} = {𝐵}) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqeq2 2750 | . . 3 ⊢ (𝐴 = 𝐵 → (𝑥 = 𝐴 ↔ 𝑥 = 𝐵)) | |
2 | 1 | abbidv 2807 | . 2 ⊢ (𝐴 = 𝐵 → {𝑥 ∣ 𝑥 = 𝐴} = {𝑥 ∣ 𝑥 = 𝐵}) |
3 | df-sn 4562 | . 2 ⊢ {𝐴} = {𝑥 ∣ 𝑥 = 𝐴} | |
4 | df-sn 4562 | . 2 ⊢ {𝐵} = {𝑥 ∣ 𝑥 = 𝐵} | |
5 | 2, 3, 4 | 3eqtr4g 2803 | 1 ⊢ (𝐴 = 𝐵 → {𝐴} = {𝐵}) |
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