设圆O与AB的切点为F
连接ID,IE ,IF
则ID =IE =IF
根据勾股定理可得AB=41
易得ID=CD=DE
设ID=x
则AF=AD=9-x,BF=BE=40-x
∴AB=AF+BF=9-x+40-x=41
2x=9+40-41
2x=8
x=4
即ID=4
设圆O与AB的切点为F
连接ID,IE ,IF
则ID =IE =IF
根据勾股定理可得AB=41
易得ID=CD=DE
设ID=x
则AF=AD=9-x,BF=BE=40-x
∴AB=AF+BF=9-x+40-x=41
2x=9+40-41
2x=8
x=4
即ID=4