∴∠FHB= 180？ -∠DFE-∠B=90？ ，∠EGB=∠DEF-∠B=30？

When point F coincides with point C, point D is just on the hypotenuse of AB.

∴DF is the height on the hypotenuse AB of RT△ABC, ∠B=30?

The side length of a triangle DEF DF=0.5BC=2.

2.DG and segment CF are always equal.

Judging from the above questions: ∠B=∠EGB=30? . ∴EB=EG

∴DG=DE-EG=2-EG

∫CF = c B- EF-EB = 2-EB

∴CF=DG

3. from the above question: CF=DG=x, and ∠D=60?

∴∠DGH=90？ -∠D=30？

∴DH=0.5DG=0.5x

Pythagorean Theorem: GH=√3/2x

∴y=S△DEF-S△DGH=√3-√3/8x？ , domain: 0≤x≤2