Solution: As shown in the figure, △DCF rotates 90 clockwise around point D to get △DAH.

The reasons are as follows: ∴△DCF≌△DHA,

∴∠fdh = 90° (rotation angle), CF=HA, DH=DF,

∫AE+CF = EF，

∴AE+HA=EF，

That is EH=EF,

At △DEH and △DEF,

DH=DFEH=EFDE=DE，

∴△DEH≌△DEF(SSS)，

∴∠EDH=∠EDF，

∴∠edf= 12∠fdh= 12×90 = 45。

So the answer is: 45.