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:
(θ为参数)的普通方程为( )
x=cosθ−1. y=sinθ+1
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
答
∵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.