Graphing Calculator's Zooming Feature
Intro  
 
 NOTES:
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notes open.
On this pages find notes on:  The Purpose of Zoom
 How to Zoom

Why Zoom?  
 


WINDOW and
ZOOM are two feaautres that facilitate viewing a graph
and reading approximate values of data from the graph using TRACE.
 WINDOW features set individual window parameters  like the leftmost x
value (Xmin) or the rightmost x value (Xmax)  and are used when one knows some information about
how a graph looks and wishes to adjust the details of the viewing screen.
 ZOOM features adjust more than one window parameter quiclky, simultaneously.
[Perhaps the speed at which this happens reminds one of the speed of a racing vehicle as it zooms by.]
Some ZOOM options are listed below. BOX  (explained below) enlarges a rectangular box on the existing graphing window.
 IN  resizes the screen in (showing more detail) on a preset scale using the curser value as a center.
 OUT  resizes the screen out (showing more of the entire graph but with less detail) on a preset scale using the curser value as a center.
 STANDARD  returns the viewing window to the default window centered at the
origin and displayed so the axes (the
xaxis and
yaxis)are square, or have the same scale.
 PREVOIUS  returns to the previously used viewing window.
 SQUARE  adjust the window, centered around the curser, so the axes are the same scale.
 Below, ZOOM BOX is described.
 
How to ZOOM BOX  
 

 1st: Store the function in the y= menu.

 2nd: Press the GRAPH key to display the graph of the function.

 3rd: Press TRACE and move to the right or left on this function to display a
decimal approximation of the x value and the y value, the value of the function.

 4th: If the decimal approximation of the y value changes in the first
two decimal digits, it is necessary to redraw the function with a different viewing
window.

 5th: Press
ZOOM then 1 for BOX to
return to the graph to select the corner of a new window.

 6th: Move the curser to a point which will serve as one corner of a new viewing window.
 I like keeping the viewing window the same shape as the viewing window of
the calculator. I pick a corner which builds this shape
rectangle about the region of the graph which needs enlargeing.

 7th: Press ENTER to make the corner "stick" and watch how the curser changes
shape on the screen.


 8th: Move the curser to the diagonally opposite corner and watch as
the new rectangular screen is created by your use of the curser.


 9th: Press ENTER to make the corner "stick" on the new corner and
watch as the graph is redrawn with better resolution.

 10th: Repeat steps 3 through 9 until curser movement does not produce a
change in the first two decimal digits of the y value.

d.) To keep a function in storage but not display the graph,
 1st: Go to the y= menu
 2nd: Move to the equal sign on the line with the desired function.
 3rd: Press ENTER (on a TI82 or TI83) so that the equal sign is no longer highlighted.
 3rd: Press Deselect (on a TI85 or TI86) on the soft key pad.
 
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