题目
若x=
π |
12 |
提问时间:2021-03-30
答案
cos4x-sin4x=(cos2x-sin2x)(cos2x+sin2x)
=cos2x-sin2x
=cos2x=cos(2×
)
=cos
=
=cos2x-sin2x
=cos2x=cos(2×
π |
12 |
=cos
π |
6 |
|