| Step | Hyp | Ref | Expression | 
						
							| 1 |  | pjidm.1 | ⊢ 𝐻  ∈   Cℋ | 
						
							| 2 | 1 | cheli | ⊢ ( 𝐴  ∈  𝐻  →  𝐴  ∈   ℋ ) | 
						
							| 3 | 1 | choccli | ⊢ ( ⊥ ‘ 𝐻 )  ∈   Cℋ | 
						
							| 4 | 3 | cheli | ⊢ ( 𝐵  ∈  ( ⊥ ‘ 𝐻 )  →  𝐵  ∈   ℋ ) | 
						
							| 5 |  | hvaddcl | ⊢ ( ( 𝐴  ∈   ℋ  ∧  𝐵  ∈   ℋ )  →  ( 𝐴  +ℎ  𝐵 )  ∈   ℋ ) | 
						
							| 6 | 2 4 5 | syl2an | ⊢ ( ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) )  →  ( 𝐴  +ℎ  𝐵 )  ∈   ℋ ) | 
						
							| 7 |  | axpjpj | ⊢ ( ( 𝐻  ∈   Cℋ   ∧  ( 𝐴  +ℎ  𝐵 )  ∈   ℋ )  →  ( 𝐴  +ℎ  𝐵 )  =  ( ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  +ℎ  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) ) ) ) | 
						
							| 8 | 1 6 7 | sylancr | ⊢ ( ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) )  →  ( 𝐴  +ℎ  𝐵 )  =  ( ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  +ℎ  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) ) ) ) | 
						
							| 9 |  | eqid | ⊢ ( 𝐴  +ℎ  𝐵 )  =  ( 𝐴  +ℎ  𝐵 ) | 
						
							| 10 |  | axpjcl | ⊢ ( ( 𝐻  ∈   Cℋ   ∧  ( 𝐴  +ℎ  𝐵 )  ∈   ℋ )  →  ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  ∈  𝐻 ) | 
						
							| 11 | 1 6 10 | sylancr | ⊢ ( ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) )  →  ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  ∈  𝐻 ) | 
						
							| 12 |  | axpjcl | ⊢ ( ( ( ⊥ ‘ 𝐻 )  ∈   Cℋ   ∧  ( 𝐴  +ℎ  𝐵 )  ∈   ℋ )  →  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) )  ∈  ( ⊥ ‘ 𝐻 ) ) | 
						
							| 13 | 3 6 12 | sylancr | ⊢ ( ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) )  →  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) )  ∈  ( ⊥ ‘ 𝐻 ) ) | 
						
							| 14 |  | simpl | ⊢ ( ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) )  →  𝐴  ∈  𝐻 ) | 
						
							| 15 |  | simpr | ⊢ ( ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) )  →  𝐵  ∈  ( ⊥ ‘ 𝐻 ) ) | 
						
							| 16 | 1 | chocunii | ⊢ ( ( ( ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  ∈  𝐻  ∧  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) )  ∈  ( ⊥ ‘ 𝐻 ) )  ∧  ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) ) )  →  ( ( ( 𝐴  +ℎ  𝐵 )  =  ( ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  +ℎ  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) ) )  ∧  ( 𝐴  +ℎ  𝐵 )  =  ( 𝐴  +ℎ  𝐵 ) )  →  ( ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  =  𝐴  ∧  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) )  =  𝐵 ) ) ) | 
						
							| 17 | 11 13 14 15 16 | syl22anc | ⊢ ( ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) )  →  ( ( ( 𝐴  +ℎ  𝐵 )  =  ( ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  +ℎ  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) ) )  ∧  ( 𝐴  +ℎ  𝐵 )  =  ( 𝐴  +ℎ  𝐵 ) )  →  ( ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  =  𝐴  ∧  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) )  =  𝐵 ) ) ) | 
						
							| 18 | 9 17 | mpan2i | ⊢ ( ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) )  →  ( ( 𝐴  +ℎ  𝐵 )  =  ( ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  +ℎ  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) ) )  →  ( ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  =  𝐴  ∧  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) )  =  𝐵 ) ) ) | 
						
							| 19 | 8 18 | mpd | ⊢ ( ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) )  →  ( ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  =  𝐴  ∧  ( ( projℎ ‘ ( ⊥ ‘ 𝐻 ) ) ‘ ( 𝐴  +ℎ  𝐵 ) )  =  𝐵 ) ) | 
						
							| 20 | 19 | simpld | ⊢ ( ( 𝐴  ∈  𝐻  ∧  𝐵  ∈  ( ⊥ ‘ 𝐻 ) )  →  ( ( projℎ ‘ 𝐻 ) ‘ ( 𝐴  +ℎ  𝐵 ) )  =  𝐴 ) |