code: func (self circle) at(phi float64) image.Point {
  	x := self.X + int(RoundFloat64(xStretch*self.radius*math.Cos(phi)))
  	y := self.Y + int(RoundFloat64(self.radius*math.Sin(phi)))
  	return image.Point{X: x, Y: y}
  }
docs: // computes the point at a given angle phi