化简：(tan10°−3)•cos10°sin50°．
问题描述：
化简：(tan10°−
)•
3
． cos10° sin50°
答
(tan10°−
)•
3
cos10° sin50°
=
(sin100−
cos100)•cos100
3
cos100•sin500
=
2(
sin100−1 2
cos100)
3
2 sin500
=
2(sin100cos600−cos100sin600) sin500
=
=-22sin(−500) sin500