select the optional third function to display (cyan) 
  This box is shown only in the case the profile contains another (third) function depending on selected variable.
  This function is plotted dependently. It means it has exactly the same scale and position as the main function (and the second function).
  The dependence mentioned above allowes precise observing of relations among the three functions.
  The definition domain of this function is not expressed. Please switch the functions if it is required.
strom