因:sinA=2√2/3, cosA=-1/3所以,sinA+cosA=(2√2-1)/3, sin(A+π/4)=sinAcosπ/4+cosAsinπ/4=√2/2sinA+√2/2cosA=√2/2(sinA+cosA)=√2/2*[(2√2-1)/3]=(4-√2)/6
