def __init__(self, **kwargs):
Coordinate.__init__(self, **kwargs)
#半径
self.radius = kwargs['radius']
#角度
self.angle = kwargs.get('angle', 90.0)
#圆心
self.center = (0, 0)
x = Geometry.sin(self.angle / 2) * self.radius
y = Geometry.cos(self.angle / 2) * self.radius
self.source = x, y
self.target = -x, y
#外切圆心，外切半径
if self.angle < 90: #三点求圆
self.wrap_center = Geometry.circle_center(self.source, self.target, self.center)
self.wrap_radius = Geometry.distance(self.wrap_center, self.center)
elif self.angle < 180: #两侧点中点
self.wrap_center = (0, y)
self.wrap_radius = x
else: #所在的圆
self.wrap_center = self.center
self.wrap_radius = self.radius
