4x-3y=-4-12t-2+12t=-6 ==> y=4/3x+2
ρ=2√2sin(θ﹣π/4)=2(sinθ-cosθ) ==> x=ρcosθ=2sinθcosθ-2cosθcosθ=sin(2θ)-cos(2θ)-1
y=ρsinθ=2sinθsinθ-2sinθcosθ=-cos(2θ)-sin(2θ)+1
(x+1)^2+(y-1)^2=2
接下来先算出圆心（-1,1）到直线的距离,然后就可以得到所截的弦长.
结果为14/5