题目：

题解：

type Solution struct {
    radius, xCenter, yCenter float64
}

func Constructor(radius, xCenter, yCenter float64) Solution {
    return Solution{radius, xCenter, yCenter}
}

func (s *Solution) RandPoint() []float64 {
    r := math.Sqrt(rand.Float64())
    sin, cos := math.Sincos(rand.Float64() * 2 * math.Pi)
    return []float64{s.xCenter + r*cos*s.radius, s.yCenter + r*sin*s.radius}
}