极坐标 (21 15:56:21)

1个回答

  • (1)(x-√3/4)²+(y-1/4)²=1/4 (2)ρ=2√(2+2cosθ) (3)B

    (1)

    x=ρcosθ=sin(θ+π/3)cosθ

    y=ρsinθ=sin(θ+π/3)sinθ

    对x,y分别积化和差有:

    x=1/2*[sin(2θ+π/3)+sin(π/3)]=1/2*[sin(2θ+π/3)+√3/2]

    y=1/2*[cos(π/3)-cos(2θ+π/3)]

    移项整理有:

    2x-√3/2=sin(2θ+π/3)

    2y-1/2=cos(2θ+π/3)

    故(2x-√3/2)²+(2y-1/2)²=1整理即有:

    (x-√3/4)²+(y-1/4)²=1/4

    (2)原方程可划为:(x-2)²+y²=4

    可令:x=2+2cosθ,y=2sinθ,

    则由:ρ=√(x²+y²)=√(4x)=2√(2+2cosθ)

    (3)由ρcosθ=2可知:x=ρcosθ=2,与θ=π/4对称,即求反函数,

    x=2 的反函数为y=2,计算一下可知答案为B