code: def _get_unit_vector_x(
      sat_sun_vec, unit_vector_z, angle_between_earth_and_sun
  ):
      beta = angle_between_earth_and_sun
      sin_beta = np.sin(beta)
      cos_beta = np.cos(beta)
      cross1 = _get_uz_cross_satsun(unit_vector_z, sat_sun_vec)
      cross2 = cross_product(cross1, unit_vector_z)
      unit_vector_x = Vector3D(
          x=sin_beta * cross1.x + cos_beta * cross2.x,
          y=sin_beta * cross1.y + cos_beta * cross2.y,
          z=sin_beta * cross1.z + cos_beta * cross2.z,
      )
      return normalize_vector(unit_vector_x)
  
imports: from collections import namedtuple
  import dask.array
  import numba
  import numpy
  from satpy.utils import get_legacy_chunk_size
label_desc: Use image node_id 19 for calling a global function with example usage: _get_unit_vector_x(sat_sun_vec, unit_vector_z, angle_between_earth_and_sun) and returns: normalize_vector