sin10*sin50*sin70 =cos80*cos40*(cos20*sin20)/sin20 =cos80*(cos40*sin40)/(2sin20) =cos80*sin80/(4sin20) =sin160/(8sin20) =1/8
sin10*sin50*sin70等于多少?知道的帮帮忙
sin10*sin50*sin70 =cos80*cos40*(cos20*sin20)/sin20 =cos80*(cos40*sin40)/(2sin20) =cos80*sin80/(4sin20) =sin160/(8sin20) =1/8