Every point of the shape must move:
-
the same distance
-
in the same direction.
Symmetry for the point (a,b)
(X,Y)
↓ -(a,b)
(X-a,Y-b)
↓ moving for (0,0)
(a-X,b-Y)
↓ +(a,b)
(2a-X,2b-Y)
Every point of the shape must move:
(X,Y)
↓ -(a,b)
(X-a,Y-b)
↓ moving for (0,0)
(a-X,b-Y)
↓ +(a,b)
(2a-X,2b-Y)