如图,线段AB是⊙O的直径,弦CD⊥AB,∠CAB=20°,则∠AOD等于____.
下图反映了哪一朝代的行政制度( )
— I was reading a novel.
附: K2=n(ad−bc)2(a+b)(c+d)(a+c)(b+d)
P(K2≥k0)
0.100
0.050
0.010
0.001
k0
2.706
3.841
6.635
10.828