17 lines
326 B
Text
17 lines
326 B
Text
|
import algebra.group
|
||
|
|
open path_algebra
|
||
|
|
|
||
|
|
variable {A : Type}
|
||
|
|
variable [s : add_comm_group A]
|
||
|
|
include s
|
||
|
|
|
||
|
|
theorem add_minus_cancel_left1 (a b c : A) : (c + a) - (c + b) = a - b :=
|
||
|
|
begin
|
||
|
|
rotate_left 1,
|
||
|
|
apply sorry
|
||
|
|
end
|
||
|
|
|
||
|
|
theorem add_minus_cancel_left2 (a b c : A) : (c + a) - (c + b) = a - b :=
|
||
|
|
by rotate_left 1;
|
||
|
|
apply sorry
|