code: def _hc(k, cs, rho, omega):
      return (
          cs
          / sin(omega)
          * (rho**k)
          * sin(omega * (k + 1))
          * greater(k, -1)
      )
  
imports: from __future__ import division, print_function, absolute_import
  from scipy._lib.six import xrange
  from numpy import logical_and, asarray, pi, zeros_like, piecewise, array, arctan2, tan, zeros, arange, floor
  from numpy.core.umath import sqrt, exp, greater, less, cos, add, sin, less_equal, greater_equal
  from .spline import cspline2d, sepfir2d
  from scipy.special import comb, gamma
label_desc: Use image node_id 9 for calling a global function with example usage: _hc(k, cs, rho, omega) and returns: unknown