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Description: An associative cancellation law for groups. (Contributed by Paul Chapman, 17-Apr-2009) (Revised by AV, 30-Aug-2021)
| Ref | Expression | ||
|---|---|---|---|
| Hypotheses | grplcan.b | ⊢ 𝐵 = ( Base ‘ 𝐺 ) | |
| grplcan.p | ⊢ + = ( +g ‘ 𝐺 ) | ||
| grpasscan1.n | ⊢ 𝑁 = ( invg ‘ 𝐺 ) | ||
| Assertion | grpasscan2 | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) → ( ( 𝑋 + ( 𝑁 ‘ 𝑌 ) ) + 𝑌 ) = 𝑋 ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | grplcan.b | ⊢ 𝐵 = ( Base ‘ 𝐺 ) | |
| 2 | grplcan.p | ⊢ + = ( +g ‘ 𝐺 ) | |
| 3 | grpasscan1.n | ⊢ 𝑁 = ( invg ‘ 𝐺 ) | |
| 4 | simp1 | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) → 𝐺 ∈ Grp ) | |
| 5 | simp2 | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) → 𝑋 ∈ 𝐵 ) | |
| 6 | 1 3 | grpinvcl | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑌 ∈ 𝐵 ) → ( 𝑁 ‘ 𝑌 ) ∈ 𝐵 ) |
| 7 | 6 | 3adant2 | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) → ( 𝑁 ‘ 𝑌 ) ∈ 𝐵 ) |
| 8 | simp3 | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) → 𝑌 ∈ 𝐵 ) | |
| 9 | 1 2 | grpass | ⊢ ( ( 𝐺 ∈ Grp ∧ ( 𝑋 ∈ 𝐵 ∧ ( 𝑁 ‘ 𝑌 ) ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) ) → ( ( 𝑋 + ( 𝑁 ‘ 𝑌 ) ) + 𝑌 ) = ( 𝑋 + ( ( 𝑁 ‘ 𝑌 ) + 𝑌 ) ) ) |
| 10 | 4 5 7 8 9 | syl13anc | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) → ( ( 𝑋 + ( 𝑁 ‘ 𝑌 ) ) + 𝑌 ) = ( 𝑋 + ( ( 𝑁 ‘ 𝑌 ) + 𝑌 ) ) ) |
| 11 | eqid | ⊢ ( 0g ‘ 𝐺 ) = ( 0g ‘ 𝐺 ) | |
| 12 | 1 2 11 3 | grplinv | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑌 ∈ 𝐵 ) → ( ( 𝑁 ‘ 𝑌 ) + 𝑌 ) = ( 0g ‘ 𝐺 ) ) |
| 13 | 12 | 3adant2 | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) → ( ( 𝑁 ‘ 𝑌 ) + 𝑌 ) = ( 0g ‘ 𝐺 ) ) |
| 14 | 13 | oveq2d | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) → ( 𝑋 + ( ( 𝑁 ‘ 𝑌 ) + 𝑌 ) ) = ( 𝑋 + ( 0g ‘ 𝐺 ) ) ) |
| 15 | 1 2 11 | grprid | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ) → ( 𝑋 + ( 0g ‘ 𝐺 ) ) = 𝑋 ) |
| 16 | 15 | 3adant3 | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) → ( 𝑋 + ( 0g ‘ 𝐺 ) ) = 𝑋 ) |
| 17 | 10 14 16 | 3eqtrd | ⊢ ( ( 𝐺 ∈ Grp ∧ 𝑋 ∈ 𝐵 ∧ 𝑌 ∈ 𝐵 ) → ( ( 𝑋 + ( 𝑁 ‘ 𝑌 ) ) + 𝑌 ) = 𝑋 ) |