Beginning Skills:  Window alterations

 

  1. Press the WINDOW key on the top row to see this screen:
    These numbers are the dimensions for the standard graphing screen.wpeC.jpg (5737 bytes)
       Xmin = left edge of the screen
       Xmax = right edge of the screen
       Xscl = scale- each mark on
                  the axis = this value
       Ymin = bottom edge of screen
  2.      Ymax = top edge of screen
                                   Yscl = scale- each mark on
                                              the axis = this value
                                   Xres = resolution-- do not alter.
  3. Often after Zooming or setting a window, the axes look double width or have dotted lines next to them.  This is a scaling problem that may be fixed two ways:

    FIRST WAY:  Setting the scales = 0 will turn off the axes markings.   Use this when the Range or Domain are large or very small and the scale isn't critical to the solution.

    SECOND WAY: If you want or need markings, find the difference between max and min, then divide by 20 or 25, rounding to a whole number.
    For example:  if Xmax = 400, and Xmin = -200, the difference = 600.   600 divided by 20 = 30, so Xscl = 30 and each mark on the x-axis = 30 units.


              
    3.    How to choose the correct window is a difficult concept for some students.
    Sometimes the problem gives Domain and Range.
           Plug the given values in-- Domain = x-values,
                                                    Range = y-values.
    Sometimes the problem gives only Domain.
                                     Use the Domain as the x-values
                                                       Use ZoomFit or use trial and error
                                      to get a good graph.
    Sometimes the problem only implies the Domain and Range.
            Use math skills:
                            For example, radicals must have positive radicands (Domain restriction) and are always positive values (Range restriction).

            Use common sense: 
                             If the problem is about bacteria counts,it must be a positive number (Domain). Read carefully and think about the context of the problem.