A:which wa
B:it wa
C:which were
D:them were
已知α为钝角,且cos(π2+α)=﹣35,则sin2α=____
某校七年级学生分两组进行“知我绍兴 爱我绍兴”的社会调查活动,阅读下列部分调查成果,回答问题。