如图AB是圆O的直径,C是AB延长线上一点,CD切圆O与D,DE⊥OC与E,又CD=4,圆O半径为3,
AB是圆O的直径,C是AB延长线上一点,CD切圆O与D,DE⊥OC与E,又CD=4,圆O半径为3,则OE长为