α∈（0,π/2）sin(a/2)>0,cos(a/2)>0y=√(1+sinα)+√(1-sinα)-√(2+2cosα)=√[sin(a/2)+cos(a/2)]^2+√[sin(a/2)-cos(a/2)]^2-√[2*2cos^2(a/2)]=sin(a/2)+cos(a/2)+|sin(a/2)-cos(a/2)|-2cos(a/2)若α∈（0,π/...