sin10°sin50°sin70° 怎样化简求值?
问题描述：
sin10°sin50°sin70° 怎样化简求值?
答
sin10°sin50°sin70°=1/2(2cos10°sin10°sin50°sin70°）/cos10°
=1/2(sin20°cos20°sin50°）/cos10°=1/4(sin40°cos40°）/cos10°
=1/8sin80°/cos10°=1/8cos10°/cos10°=1/8