[] , [] , [^] , []Sum of segments / Change the condition(GC World : Various Problems ,Constant)
DE + DF did not change when I moved point D.
How will this result change if the shape of triangle was changed?
Let's explore after moving point A.
What will occur in this case?
Which parts of your proof are available and not available?

GC/Win


Forum of Geometric Constructor by Y.Iijima