He's gone to the library ,_______ he ?
A:isn't
B:doesn't
C:hasn't
D:wasn't
如图,点D(0,3),O(0,0),C(4,0)在⊙A上,BD是⊙A的一条弦,则sin∠OBD=( )
选词填空。
wasp crisp
分解因式:
(1)12x2﹣3y2
(2)3ax2﹣6axy+3ay2.