题目已知BCBCBC是⊙O\odot O⊙O的直径,点DDD是BCBCBC延长线上一点,AB=ADAB=ADAB=AD,AEAEAE是⊙O\odot O⊙O的弦,∠AEC=30∘\angle AEC=30^{\circ}∠AEC=30∘.(1)(1)(1)求∠BAC\angle BAC∠BAC的度数;(2)(2)(2)求证:直线ADADAD是⊙O\odot O⊙O的切线;(3)(3)(3)若AE⊥BCAE\bot BCAE⊥BC,垂足为点MMM,⊙O\odot O⊙O的半径为444,求AEAEAE的长.知识点:切线的判定章节:图形的性质 / 圆