code: def dip_direction2strike(azimuth):
      
      azimuth = parse_azimuth(azimuth)
      strike = azimuth - 90
      if strike < 0:
          strike += 360
      return strike
docs: Converts a planar measurment of dip direction using the dip-azimuth
      convention into a strike using the right-hand-rule.
  
      Parameters
      ----------
      azimuth : number or string
          The dip direction of the plane in degrees. This can be either a
          numerical azimuth in the 0-360 range or a string representing a quadrant
          measurement (e.g. N30W).
  
      Returns
      -------
      strike : number
          The strike of the plane in degrees following the right-hand-rule.