神马作文网三角函数 (14 16:20:17)
来源：学生作业帮 编辑：神马作文网作业帮 分类：数学作业 时间：2024/11/11 15:28:20
三角函数 (14 16:20:17)
sin6°sin42°sin66°sin78°
sin6°sin42°sin66°sin78°
sin6sin42sin66sin78
=sin6(sin78=cos12)(sin78=cos24)(sin42=cos48)
=sin6cos12*cos24cos48 =sin6cos6cos12*cos24cos48/cos6
=1/(2sin6cos61/2*2cos12*1cos24*2cos48/cos6 =1/2*1/2sin12*2cos12*cos24*cos48/cos6 =1/4*1/2sin24*cos24*cos48/cos6 =1/8*1/2sin48*2cos48/cos6
=1/16sin96/cos6(sin96=cos6)
=1/16
=sin6(sin78=cos12)(sin78=cos24)(sin42=cos48)
=sin6cos12*cos24cos48 =sin6cos6cos12*cos24cos48/cos6
=1/(2sin6cos61/2*2cos12*1cos24*2cos48/cos6 =1/2*1/2sin12*2cos12*cos24*cos48/cos6 =1/4*1/2sin24*cos24*cos48/cos6 =1/8*1/2sin48*2cos48/cos6
=1/16sin96/cos6(sin96=cos6)
=1/16