题目如图,△ABD\triangle ABD△ABD是⊙O⊙O⊙O的内接三角形,ABABAB是⊙O⊙O⊙O的直径,点EEE为\overparenBD\overparen{BD}\overparenBD的中点,延长BABABA到点CCC,并连结CDCDCD,且∠CDA=∠B.∠CDA=∠B.∠CDA=∠B.(1)(1)(1)求证:CDCDCD是⊙O⊙O⊙O的切线;(2)(2)(2)若DE=3DE=3DE=3,AB=6AB=6AB=6,填空;①∠BDE=∠BDE=∠BDE=______°°°;②线段CDCDCD的长为 ______;知识点:切线的判定与性质章节:图形的性质 / 圆