1) because the angle GEF= angle FED is the same after folding.

Angle GFE= feed angle with the same internal dislocation angle (AD//BC)

So angle GEF= angle GFE, so triangle EFG is an isosceles triangle.

That is, the overlapping part shape triangle EFG is an isosceles triangle.

2) Angle AED' = 180-2 Angle EFB =180-1/kloc-0 = 70 degrees.

3) Because angle AEF+ angle EFB= 180, that is, angle AEG+ angle GEF+ angle EFB= 180.

Therefore, the relationship between Angle ·EFB and Angle and is:

Angle EFB+2 Angle AED' = 180