cosπ/8·cos3π/8计算过程
问题描述：
cosπ/8·cos3π/8计算过程
答
cos(π/8)×cos(3π/8)
=cos[(π/2)－(3π/8)]×cos(3π/8)
=sin(3π/8)cos(3π/8)
=(1/2)[2sin(3π/8)cos(3π/8(]
=(1/2)sin(3π/4)
=√2/4