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Graphing Calculator: Zoom Features
The key is a very useful tool for changing the view of your graph. When you press there are 10 options available from the Zoom menu (you can only see the fist seven on your screen).

Options 4 – 7 and 10 change the viewing window to automatic built in settings. For more on windows, reference the lesson on setting windows.
  • Option 4: Zdecimal creates a window of x:[-4.7, 4.7] x 1 (read as xscl = 1 or by 1) and y:[-3.1, 3.1] x 1 (read as yscl = 1 or by 1). This is another form of the "friendly" window that displays nice x and y values while tracing. It is based on the dimensions and number of pixels on the graph screen.
  • Option 5: Zsquare "squares up" the window. Because the viewing window is not the same in both the x and y direction, when you try to graph a circle, it looks like an ellipse. Using Zsquare eliminates this problem. This is usually used just when graphing circles.
  • Option 6: Zstandard sets the window as [-10, 10 ] x 1 in both directions.
  • Option 7: Ztrig sets a window that is useful in graphing trigonometric functions. The values it uses are in radians, so be aware that your mode should be in radians when graphing trig functions and using this setting. For more on calculator modes, click here to go to the mode lesson.
  • Option 9: ZoomStat is helpful when using StatPlots. Once you have data entered into lists and a plot turned on, ZoomStat automatically sets a window to fit the data. To learn more about entering data into lists, click here to see the data entry lesson.
  • Option 10: ZoomFit (at the bottom of the list) is helpful if you know the appropriate xmin and xmax values for your function. Based on your input of xmin and xmax, the calculator will calculate the ymin and ymax values. This can be a useful tool when working with functions that require drastic changes in the window settings. However, it may not always give a graph you like.
Options 1, 2, 3, and 8 from the Zoom menu redefine the window based on your placement of the cursor. These are seldom used, so we will not discuss them here. For more information, see your User’s Guide.
As an example, let's enter y1 = 5x4 - 2x2 +17x - 57 into the calculator. This function cannot be viewed completely in a friendly or standard window.



It appears that our xmin and xmax of –9.4 and 9.4 respectively are OK. We just need to change the y values. By using ZoomFit, we get



It is difficult to see the zeros of this function with the new window settings of



But it does provide us the useful information if we want to reset the window ourselves to



The extremely large ymin calculated by ZoomFit was to accommodate x values of –10 and 10. When you plug those numbers into the function, you get 49913. To see an appropriate graph, we don’t need those extreme values. So ZoomFit should be used with caution and the window adjusted afterward if necessary.

Your most useful tools will most likely be the ZoomStandard feature to reset the window after making adjustments and the ZoomStat feature when graphing statistical data.



S Taylor

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