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