Description: First-order logic and set theory. (Contributed by Jonathan Ben-Naim, 3-Jun-2011) (New usage is discouraged.)
Ref | Expression | ||
---|---|---|---|
Hypothesis | bnj931.1 | ⊢ 𝐴 = ( 𝐵 ∪ 𝐶 ) | |
Assertion | bnj931 | ⊢ 𝐵 ⊆ 𝐴 |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | bnj931.1 | ⊢ 𝐴 = ( 𝐵 ∪ 𝐶 ) | |
2 | ssun1 | ⊢ 𝐵 ⊆ ( 𝐵 ∪ 𝐶 ) | |
3 | 2 1 | sseqtrri | ⊢ 𝐵 ⊆ 𝐴 |