cos43°cos77°+sin43°cos167°的值为( ) A.1 B.12 C.[−12,12] D.12
问题描述:
cos43°cos77°+sin43°cos167°的值为( )
A. 1
B.
1 2
C. [−
,1 2
]1 2
D.
1 2
答
cos43°cos77°+sin43°cos167°
=cos43°cos77°-sin43°sin77°
=cos120°
=-
.1 2
故选:D.