The angle ACB is equal to 90 degrees, CD is the bisector of the angle,

∴∠ACD=∠BCD=45

∠A=90 -∠B

∵EF⊥AB

∴∠F=90 -∠EDF=90 -∠ADC

∠ ADC =∠ BCD +∠ B = 45 +∠ B。

∴∠F=90 -(45 +∠B)=45 -∠B

∠∠ECB =∠B

∴∠dce=∠bcd-∠ecb=45-∞b

∴∠F=∠DCE