证明2cos^2(π/4-α/2)=1+sinα
问题描述：
证明2cos^2(π/4-α/2)=1+sinα
答
由cos2x=2*(cosx)^2-1得2*(cosx)^2=cos2x+1
2cos^2(π/4-α/2)
=cos(π/2-α)+1
=sinα+1
答
2cos^2(π/4-α/2)
=cos2(π/4-α/2)+1
=cos(π/2-α)+1
=sinα+1