Question

COS43°COS77°+SIN43°COS167°等于什么啊？

Answer 1

COS43°COS77°+SIN43°COS167°=COS43°COS77°+SIN43°COS13°=COS43°COS77°+SIN43°SIN77°=COS120°=-0.5

Answer 2

解：原式=COS43°COS77°-SIN43°SIN77°
=cos(43°+77°)
=cos120°
=-cos60°
=-0.5

Answer 3

-0.5