Beginning Skills: Window alterations
- Press the WINDOW key on the top row to see this screen:
These numbers are the dimensions for the standard graphing screen.
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
- Ymax = top edge of screen
Yscl
= scale- each mark on
the
axis = this value
Xres
= resolution-- do not alter.
- 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.