设直线上三点分别为:(x1,y1),(x2,y2),(x3.y3)
它们在一条直线上时满足:(y2-y1)/(x2-x1)=(y3-y1)/(x3-x1)
化简后得:(x2y3-y2x3)+(x3y1-y3x1)+(x1y2-y1x2)=0
将 x1=ρ1cosθ1 y1=ρ1sinθ1
x2=ρ2cosθ2 y2=ρ2sinθ2
x3=ρ3cosθ3 y3=ρ3sinθ3
带入,化简即得:sin(θ2-θ3)/ρ1+ sin(θ3-θ1)/ρ2+ sin(θ1-θ2)/ρ3=0
设直线上三点分别为:(x1,y1),(x2,y2),(x3.y3)
它们在一条直线上时满足:(y2-y1)/(x2-x1)=(y3-y1)/(x3-x1)
化简后得:(x2y3-y2x3)+(x3y1-y3x1)+(x1y2-y1x2)=0
将 x1=ρ1cosθ1 y1=ρ1sinθ1
x2=ρ2cosθ2 y2=ρ2sinθ2
x3=ρ3cosθ3 y3=ρ3sinθ3
带入,化简即得:sin(θ2-θ3)/ρ1+ sin(θ3-θ1)/ρ2+ sin(θ1-θ2)/ρ3=0