Graphing Calculator's Zooming Features, Zoom Box

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Graphing Calculator's Zooming Feature

Intro

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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 left-most x value (Xmin) or the right-most 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 x-axis and y-axis)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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