cos80°cos35°+sin80°cos55°的值是( ) A.22 B.-22 C.12 D.-12
问题描述:
cos80°cos35°+sin80°cos55°的值是( )
A.
2
2
B. -
2
2
C.
1 2
D. -
1 2
答
cos80°cos35°+sin80°cos55°
=cos(80°-35°)
=cos45°
=
.
2
2
故选A