Description: Signed area is linear by the second argument. (Contributed by Saveliy Skresanov, 19-Sep-2017)
Ref | Expression | ||
---|---|---|---|
Hypothesis | sigar | |
|
Assertion | sigarls | |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | sigar | |
|
2 | simp1 | |
|
3 | 2 | cjcld | |
4 | simp2 | |
|
5 | simpr | |
|
6 | 5 | recnd | |
7 | 6 | 3adant1 | |
8 | 3 4 7 | mulassd | |
9 | 8 | fveq2d | |
10 | simp3 | |
|
11 | 3 4 | mulcld | |
12 | 10 11 | immul2d | |
13 | 11 7 | mulcomd | |
14 | 13 | fveq2d | |
15 | imcl | |
|
16 | 15 | recnd | |
17 | 11 16 | syl | |
18 | 17 7 | mulcomd | |
19 | 12 14 18 | 3eqtr4d | |
20 | 9 19 | eqtr3d | |
21 | simpl | |
|
22 | 21 6 | mulcld | |
23 | 22 | 3adant1 | |
24 | 1 | sigarval | |
25 | 2 23 24 | syl2anc | |
26 | 1 | sigarval | |
27 | 26 | 3adant3 | |
28 | 27 | oveq1d | |
29 | 20 25 28 | 3eqtr4d | |