xsinθ+ycosθ-1=0
点P(2,2)到直线距离
=|2sinθ+2cosθ-1|/根号下(sin²θ+cos²θ)
=|2sinθ+2cosθ-1|
=|2根号下2sin(θ+π/4)-1|
当 sin(θ+π/4)=-1
2根号下2sin(θ+π/4)-1取得最小值
|2根号下2sin(θ+π/4)-1|取得最大值=2根号下2+1