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Mirrors > Home > MPE Home > Th. List > sseqtri | Structured version Visualization version GIF version |
Description: Substitution of equality into a subclass relationship. (Contributed by NM, 28-Jul-1995.) |
Ref | Expression |
---|---|
sseqtr.1 | ⊢ 𝐴 ⊆ 𝐵 |
sseqtr.2 | ⊢ 𝐵 = 𝐶 |
Ref | Expression |
---|---|
sseqtri | ⊢ 𝐴 ⊆ 𝐶 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | sseqtr.1 | . 2 ⊢ 𝐴 ⊆ 𝐵 | |
2 | sseqtr.2 | . . 3 ⊢ 𝐵 = 𝐶 | |
3 | 2 | sseq2i 3954 | . 2 ⊢ (𝐴 ⊆ 𝐵 ↔ 𝐴 ⊆ 𝐶) |
4 | 1, 3 | mpbi 229 | 1 ⊢ 𝐴 ⊆ 𝐶 |
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