向量AB={sin(α-π/4)-cos(α-π/4),sinα-cosα,-2}
={-√2*cosα,sinα-cosα,-2}
|AB|^2=(-√2*cosα)^2+(sinα-cosα)^2+(-2)^2
=2(cosα)^2+(1-2*sinα*cosα)+4=1+cos2α+1-sin2α+4
=cos2α-sin2α+6=√2*cos(α+π/4)+6
|AB|^2的最大值为6+√2,最小值为6-√2,
所以|AB|的最大值为√(6+√2),最小值为√(6-√2).