A:同位角
B:内错角
C:同旁内角
D:邻补角
多边形的边数由4增加到8,则其外角和的度数( )
①油脂类
②果蔬类
③谷类
④鱼、肉、蛋类
⑤乳、豆类
Students used to information from newspapers or magazines, but now they are used to for it on the Internet directly.
如图,梯形ABCD中,AB∥DC,AB⊥BC,AB=2cm,CD=4cm.以BC上一点O为圆心的圆经过A、D两点,且∠AOD=90°,则圆心O到弦AD的距离是____ cm.