√cos²600º＝ A.+_√3/2 B.√3/2 C.-√3/2 D.1/2

题目

√cos²600º＝ A.+_√3/2 B.√3/2 C.-√3/2 D.1/2

答案

解由√cos²600º
=/cos600º/
=/cos(720°-120°)/
=/cos(-120°)/
=/cos120°/
=/-cos60°/
=/-1/2/
=1/2
故选D