1
pcos(θ-π/3)=a x=a的参数方程pcosθ=a,pcos0=pcos(π/3-π/3)逆时针转过π/3得到
2
pcos(θ-π/3)=a顺时针旋转π/3,令θ‘=θ-π/3,pcos(θ-π/3)=pcosθ'=a, x=a
3
(1,√3)在I象限,ρ的取值与象限无关,一般将点到O(0,0)距离作为ρ,即ρ=√(x^2+y^2)>0
θ取值一般是以O(0,0)为中心,逆时针旋转为正方向请问怎么样把pcos（θ-π/3）=a用三角函数花开来然后用x=pcosθ，y=psinθ代入得到方程？谢谢pcosθ=x,psinθ=ypcos(θ-π/3)=pcosθcos(π/3)-psinθsin(π/3)=pcosθ/2-√3psinθ/2=x/2-√3y/2=a旋转-π/3 x'=xcos(-π/3)+ysin(-π/3)y'=xsin(-π/3)+ycos(-π/3)x'=a