OD=R=5

∫AB average score ∠BAC

∴∠BAD=∠DAC

∴ arc BD= arc CD

∴OD⊥BC and Belgium = EC

Ab is the diameter.

∠C = 90°

∴OE‖AC

OE/AC=OB/AB= 1/2

OE= 1/2AC=3

DE=OD-OE=2