— Will you attend the meeting this afternoon?— But I __________ anything about it yet.
A:wasn't told
B:haven't been told
C:didn't tell
D:won't tell
实验序号
入射角
反射角
1
60°
30°
2
40°
50°
3
10°
80°
若cosπ+α=-13,则cosα的值为( )