sin4(π/8)+cos4(π/8)的值,
问题描述：
sin4(π/8)+cos4(π/8)的值,
答
sin4(π/8)+cos4(π/8)
=[1-cos(π/4)]²/4＋[1+cos(π/4)]²/4
=[2+2cos²(π/4)]/4
=[2+1+cos(π/2)]/4
=3/4