cos2π/7cos4π/7cos8π/7要过程

问题描述:

cos2π/7cos4π/7cos8π/7要过程

8sin2π/7cos2π/7cos4π/7cos8π/7/(8sin2π/7)
=4sin4π/7cos4π/7cos8π/7/(8sin2π/7)
=2sin8π/7cos8π/7/(8sin2π/7)
=sin16π/7/(8sin2π/7)
=sin2π/7/(8sin2π/7)
=1/8