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Description: The identity element of a group belongs to the group. (Contributed by Thierry Arnoux, 4-May-2026)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | grpidcld.1 | ⊢ 𝐵 = ( Base ‘ 𝐺 ) | |
| grpidcld.2 | ⊢ 0 = ( 0g ‘ 𝐺 ) | ||
| grpidcld.3 | ⊢ ( 𝜑 → 𝐺 ∈ Grp ) | ||
| Assertion | grpidcld | ⊢ ( 𝜑 → 0 ∈ 𝐵 ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | grpidcld.1 | ⊢ 𝐵 = ( Base ‘ 𝐺 ) | |
| 2 | grpidcld.2 | ⊢ 0 = ( 0g ‘ 𝐺 ) | |
| 3 | grpidcld.3 | ⊢ ( 𝜑 → 𝐺 ∈ Grp ) | |
| 4 | 1 2 | grpidcl | ⊢ ( 𝐺 ∈ Grp → 0 ∈ 𝐵 ) |
| 5 | 3 4 | syl | ⊢ ( 𝜑 → 0 ∈ 𝐵 ) |