sin6sin42sin66sin78
=sin6cos48cos24cos12
=2sin6cos6cos12cos24cos48/2cos6
=sin12cos12cos24cos48/2cos6
=sin24cos24cos48/4cos6
=sin48cos48/8cos6
=sin96/16cos6
=cos6/16cos6
=1/16
sin6sin42sin66sin78
=sin6cos48cos24cos12
=2sin6cos6cos12cos24cos48/2cos6
=sin12cos12cos24cos48/2cos6
=sin24cos24cos48/4cos6
=sin48cos48/8cos6
=sin96/16cos6
=cos6/16cos6
=1/16