cos12度*cos24度*cos48度*cos84度=什么?

cos84=-cos96
代入原式=-cos12*cos24*cos48*cso96
=-sin12*cos12*cos24*cos48*cso96/sin12(先乘sin12再除sin12)
=-0.5*sin24*cos24*cos48*cos96/sin12
=-0.25*sin48*cos48*cos96/sin12
=-0.125*sin96*cos96/sin12
=-0.0625*sin192/sin12
=0.0625=1/16