sin10°sin30°sin50°sin70°的值为( ) A.12 B.14 C.18 D.116
问题描述:
sin10°sin30°sin50°sin70°的值为( )
A.
1 2
B.
1 4
C.
1 8
D.
1 16
答
原式=
•1 2
=2sin10°cos10°cos20°cos40° 2cos10°
=sin80° 16cos10°
1 16
故选D.