x = r cosα, y = r sinα
r = √(x² + y²), cosα = x/r
r = 2(1 - cosα)
r² = 2r - 2x
x² + y² + 2x - 2√(x² + y²) = 0
x = r cosα, y = r sinα
r = √(x² + y²), cosα = x/r
r = 2(1 - cosα)
r² = 2r - 2x
x² + y² + 2x - 2√(x² + y²) = 0