证明:(1)连接OC,OE,
∵AD与⊙O相切于E点,AB与⊙O相切于C点,
∴AE=AC,OE⊥AD,OC⊥AB,
∴AE=ED,AC=CB,
∴AB=AD;
(2)方法一:连接OD、OB∵OE=OC(小圆半径)
OD=OB(大圆半径)OE⊥AD OC⊥AB
有勾股定理可知DE=BC
方法二:因为AB=AD 且切线AC=AE ∴AD-AE=AC-AB∴DE=BC
证明:(1)连接OC,OE,
∵AD与⊙O相切于E点,AB与⊙O相切于C点,
∴AE=AC,OE⊥AD,OC⊥AB,
∴AE=ED,AC=CB,
∴AB=AD;
(2)方法一:连接OD、OB∵OE=OC(小圆半径)
OD=OB(大圆半径)OE⊥AD OC⊥AB
有勾股定理可知DE=BC
方法二:因为AB=AD 且切线AC=AE ∴AD-AE=AC-AB∴DE=BC