∠DOE= ∠DOB-∠EOB =
∠AOB/2 -∠COB/2 =
∠AOB/2 -(∠AOB-∠AOC)/2 =
∠AOB/2 -∠AOB/2 +∠AOC/2 =
∠AOC/2 =90°/2 =45°
∠DOE= ∠DOB-∠EOB =
∠AOB/2 -∠COB/2 =
∠AOB/2 -(∠AOB-∠AOC)/2 =
∠AOB/2 -∠AOB/2 +∠AOC/2 =
∠AOC/2 =90°/2 =45°