cos^2-π/8-1/2=?
问题描述:
cos^2-π/8-1/2=?
答
cos^2-π/8-1/2
=cos^2(π/8)-1/2
=[1+cos2(π/8)]/2-1/2
=[1+cos(π/4)]/2-1/2
=1/2+√2/4-1/2
=(√2)/4