三角函数 (14 16:20:17)sin6°sin42°sin66°sin78°

其实很简单，就是角度的准换
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度*sin42度*sin66度*sin78度 *cos6度/cos6度
=sin6度cos6度cos12度cos24度cos48/cos6度
=1/2sin12度cos12度cos24度cos48/cos6度
=1/16sin96/cos6度
=1/16

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