曲线C:x=cosθ−1.y=sinθ+1(θ为参数)的普通方程为(  ) A.(x-1)2+(y+1)2=1 B.(x+1)2+(y+1)2=1 C.(x+1)2+(y-1)2=1 D.(x-1)2+(y-1)2=1

问题描述:

曲线C:

x=cosθ−1.
y=sinθ+1
(θ为参数)的普通方程为(  )
A. (x-1)2+(y+1)2=1
B. (x+1)2+(y+1)2=1
C. (x+1)2+(y-1)2=1
D. (x-1)2+(y-1)2=1

∵曲线C:

x=cosθ−1.
y=sinθ+1

x+1=cosθ
y−1=sinθ

∴cos2θ+sin2θ=(x+1)2+(y-1)2=1,
故选C.