问一下老师是不是应该这样α∈(0,π/2),
sinα=4/5,所以cosα=3/5,
sin(α+π/4)-√2cos(π-α)=sinα*cosπ/4+cosα*sinπ/4+√2cosα
=(√2/2)*(4/5+3/5)+√2*3/5
=(13*√2)/10