'Returns the length of the sides.
The half-length of the side and the apothem form two legs
of a right triangle whose hypotenuse is the radius of the
regular polygon.
Examples
>>> from sympy.geometry import RegularPolygon
>>> from sympy import sqrt
>>> s = square_in_unit_circle = RegularPolygon((0, 0), 1, 4)
>>> s.length
sqrt(2)
>>> sqrt((_/2)**2 + s.apothem**2) == s.radius
True'

@property
def length(self):

    return ((self.radius * 2) * sin((pi / self._n)))
