Metamath Proof Explorer


Theorem sigarls

Description: Signed area is linear by the second argument. (Contributed by Saveliy Skresanov, 19-Sep-2017)

Ref Expression
Hypothesis sigar G=x,yxy
Assertion sigarls ABCAGBC=AGBC

Proof

Step Hyp Ref Expression
1 sigar G=x,yxy
2 simp1 ABCA
3 2 cjcld ABCA
4 simp2 ABCB
5 simpr BCC
6 5 recnd BCC
7 6 3adant1 ABCC
8 3 4 7 mulassd ABCABC=ABC
9 8 fveq2d ABCABC=ABC
10 simp3 ABCC
11 3 4 mulcld ABCAB
12 10 11 immul2d ABCCAB=CAB
13 11 7 mulcomd ABCABC=CAB
14 13 fveq2d ABCABC=CAB
15 imcl ABAB
16 15 recnd ABAB
17 11 16 syl ABCAB
18 17 7 mulcomd ABCABC=CAB
19 12 14 18 3eqtr4d ABCABC=ABC
20 9 19 eqtr3d ABCABC=ABC
21 simpl BCB
22 21 6 mulcld BCBC
23 22 3adant1 ABCBC
24 1 sigarval ABCAGBC=ABC
25 2 23 24 syl2anc ABCAGBC=ABC
26 1 sigarval ABAGB=AB
27 26 3adant3 ABCAGB=AB
28 27 oveq1d ABCAGBC=ABC
29 20 25 28 3eqtr4d ABCAGBC=AGBC