Solve the problem according to the letters in the picture.

Extend EF to the ground G, so that point E is EH vertical DE and point E is EI vertical DF.

From the meaning of the question, AB=ED.

So the two triangles ABC and DEH are equal.

Let AB=DE= radical number 3, BC=EH= 1, then AC=HD=2.

DE*EH=DH*EI (calculated by triangle area)

So EI=√ (root number) 3/2 root number three.

Since ED/EF=√2 and DE=√3.

So EF=√3/√2.

So EI/EF= 1/√2.

So ∠ IEF = 45.

Eif = 90, so ife = 45.

DHE=∠DFG=60

So ∠ EFG = 60-45 = 15, which is the inclination angle.