code: def L_plate_ET(q_plant, W_chan):
      
      L_plate = (q_plant / (num_plates_ET(q_plant, W_chan) * W_chan *
                            design.ent_tank.CAPTURE_BOD_VEL.magnitude * np.cos(
                  design.ent_tank.PLATE_ANGLE.to(u.rad).magnitude)))
      - (design.ent_tank.PLATE_S.magnitude * np.tan(design.ent_tank.PLATE_ANGLE.to(u.rad).magnitude))
      return L_plate
docs: Return the length of the plates in the entrance tank.
  
      Parameters
      ----------
      q_plant: float
          Plant flow rate
  
      W_chan: float
          Width of channel
  
      Returns
      -------
      float
          ?
  
      Examples
      --------
      >>> from aguaclara.play import*
      >>> L_plate_ET(20*u.L/u.s,2*u.m)
      0.00194