AE= 1/2*AB=√3, in △AEO, Pythagorean theorem

OE=√(R^2-AE^2)=√(4-3)= 1

DE = OD-OE = R-OE = 2- 1 = 1

(2)

ae=√(ao^2-oe^2)=√(4- 1)=√3

AB=2AE=2√3

DE=OD-OE=2- 1= 1