cos -3分之16π=A 2分之1B 根号3/2C -1/2D-根号3/2
问题描述：
cos -3分之16π=
A 2分之1
B 根号3/2
C -1/2
D-根号3/2
答
cos -3分之16π=cos 3分之16π=cos 3分之2π=cos120=-1/2
答
cos(-16π/3)
=cos(16π/3)
=cos(5π+π/3)
=-cos(π/3)
=-1/2 (选C)