如图,圆这章的题,2道,

1.
过D做DF⊥AB,交AB于F
连接BE
假设圆半径OA=OB=r
则：OB²-OD²=BD²
r²-(r-2)²=16
r=5
由△OBD的面积得
1/2OB×DF=1/2OD×BD
DF=OD×BD÷OB=3×4÷5=12/5
OF=√(OD²-DF²)=9/5
AD=√(AF²+DF²)=√[(34/5)²+(12/5)²]=2√13
2.
(1)
连接OE,则AE为圆的直径
∵OD⊥AB,BE⊥AB
∴OD∥BE
∴∠ODE=∠BED
∠AEB=∠AOC=52°
又∵OD=OE
∴∠ODE=∠OED
∴∠OED=∠BED
∴∠BED=1/2∠AEB=26°
(2)
AC=√(OA²-OC²)=√(25-9)=4
AB=2AC=8