| Step | Hyp | Ref | Expression | 
						
							| 1 |  | dvrdir.b | ⊢ 𝐵  =  ( Base ‘ 𝑅 ) | 
						
							| 2 |  | dvrdir.u | ⊢ 𝑈  =  ( Unit ‘ 𝑅 ) | 
						
							| 3 |  | dvrdir.p | ⊢  +   =  ( +g ‘ 𝑅 ) | 
						
							| 4 |  | dvrdir.t | ⊢  /   =  ( /r ‘ 𝑅 ) | 
						
							| 5 |  | simpl | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  𝑅  ∈  Ring ) | 
						
							| 6 |  | simpr1 | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  𝑋  ∈  𝐵 ) | 
						
							| 7 |  | simpr2 | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  𝑌  ∈  𝐵 ) | 
						
							| 8 | 1 2 | unitss | ⊢ 𝑈  ⊆  𝐵 | 
						
							| 9 |  | simpr3 | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  𝑍  ∈  𝑈 ) | 
						
							| 10 |  | eqid | ⊢ ( invr ‘ 𝑅 )  =  ( invr ‘ 𝑅 ) | 
						
							| 11 | 2 10 | unitinvcl | ⊢ ( ( 𝑅  ∈  Ring  ∧  𝑍  ∈  𝑈 )  →  ( ( invr ‘ 𝑅 ) ‘ 𝑍 )  ∈  𝑈 ) | 
						
							| 12 | 9 11 | syldan | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  ( ( invr ‘ 𝑅 ) ‘ 𝑍 )  ∈  𝑈 ) | 
						
							| 13 | 8 12 | sselid | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  ( ( invr ‘ 𝑅 ) ‘ 𝑍 )  ∈  𝐵 ) | 
						
							| 14 |  | eqid | ⊢ ( .r ‘ 𝑅 )  =  ( .r ‘ 𝑅 ) | 
						
							| 15 | 1 3 14 | ringdir | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  ( ( invr ‘ 𝑅 ) ‘ 𝑍 )  ∈  𝐵 ) )  →  ( ( 𝑋  +  𝑌 ) ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) )  =  ( ( 𝑋 ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) )  +  ( 𝑌 ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) ) ) ) | 
						
							| 16 | 5 6 7 13 15 | syl13anc | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  ( ( 𝑋  +  𝑌 ) ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) )  =  ( ( 𝑋 ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) )  +  ( 𝑌 ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) ) ) ) | 
						
							| 17 |  | ringgrp | ⊢ ( 𝑅  ∈  Ring  →  𝑅  ∈  Grp ) | 
						
							| 18 | 17 | adantr | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  𝑅  ∈  Grp ) | 
						
							| 19 | 1 3 | grpcl | ⊢ ( ( 𝑅  ∈  Grp  ∧  𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵 )  →  ( 𝑋  +  𝑌 )  ∈  𝐵 ) | 
						
							| 20 | 18 6 7 19 | syl3anc | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  ( 𝑋  +  𝑌 )  ∈  𝐵 ) | 
						
							| 21 | 1 14 2 10 4 | dvrval | ⊢ ( ( ( 𝑋  +  𝑌 )  ∈  𝐵  ∧  𝑍  ∈  𝑈 )  →  ( ( 𝑋  +  𝑌 )  /  𝑍 )  =  ( ( 𝑋  +  𝑌 ) ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) ) ) | 
						
							| 22 | 20 9 21 | syl2anc | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  ( ( 𝑋  +  𝑌 )  /  𝑍 )  =  ( ( 𝑋  +  𝑌 ) ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) ) ) | 
						
							| 23 | 1 14 2 10 4 | dvrval | ⊢ ( ( 𝑋  ∈  𝐵  ∧  𝑍  ∈  𝑈 )  →  ( 𝑋  /  𝑍 )  =  ( 𝑋 ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) ) ) | 
						
							| 24 | 6 9 23 | syl2anc | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  ( 𝑋  /  𝑍 )  =  ( 𝑋 ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) ) ) | 
						
							| 25 | 1 14 2 10 4 | dvrval | ⊢ ( ( 𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 )  →  ( 𝑌  /  𝑍 )  =  ( 𝑌 ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) ) ) | 
						
							| 26 | 7 9 25 | syl2anc | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  ( 𝑌  /  𝑍 )  =  ( 𝑌 ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) ) ) | 
						
							| 27 | 24 26 | oveq12d | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  ( ( 𝑋  /  𝑍 )  +  ( 𝑌  /  𝑍 ) )  =  ( ( 𝑋 ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) )  +  ( 𝑌 ( .r ‘ 𝑅 ) ( ( invr ‘ 𝑅 ) ‘ 𝑍 ) ) ) ) | 
						
							| 28 | 16 22 27 | 3eqtr4d | ⊢ ( ( 𝑅  ∈  Ring  ∧  ( 𝑋  ∈  𝐵  ∧  𝑌  ∈  𝐵  ∧  𝑍  ∈  𝑈 ) )  →  ( ( 𝑋  +  𝑌 )  /  𝑍 )  =  ( ( 𝑋  /  𝑍 )  +  ( 𝑌  /  𝑍 ) ) ) |