# TI 89 Calculus: Basic Functions in Simple Steps

Calculus > TI 89 Calculus

## TI 89 Calculus: Magnify Graphs With the TI-89 ZoomBox feature

The TI-89 guesses at what portion of the graph you want to see. Usually, you’ll have to tweak the viewing window to get a useful result. The TI-89 has several features to change the viewing window, including ZoomIn, Zoomout and ZoomStd — which displays the “standard” window from -10 to 10. ZoomBox allows you to box in a certain area of the graph and then zoom in on that portion.
Sample problem: Magnify the graph of the following function using ZoomBox feature:f(x) = 10 sin(x)

Step 1: Press HOME.

Step 2: Press the DIAMOND key and then F1 to enter the y=editor.

Step 3: Type the function into the in the “y1 =” slot of the y=editor. To enter the function, press ENTER to move down to the input line and then press 10 2ND Y x ).

Step 4: Press ENTER.

Step 5: Press the DIAMOND key and then F3 to view the graph of the function. If you can’t see the graph on your screen, set your window to display the graph. For this particular graph, you’ll be able to see the graph with the ZoomStd feature; Press F2 and then press 6.

Step 6: Press F2 and then 1 to access the ZoomBox feature.

Step 7: Select the first corner of the box by pressing the arrow keys. Press ENTER.

Step 8: Select the second corner of the box. Press ENTER.

That’s it! You’re done!

## Piecewise Functions TI 89 “when(” Command

Piecewise functions are functions that are in separate pieces. In other words, instead of one equation to input, you may have several making up one large function. While plotting (and differentiating) piecewise functions by hand can become problematic — especially if you have three or more equations to deal with — the TI89 makes graphing piecewise functions a snap with its “when(“ command.

## Piecewise Functions TI 89 “when”: Example

Sample problem: graph the following piecewise functions:

• f(x) = 3x, x is greater than 0,
• f(x) = x + 5, x is less than or equal to 0.

Step 1: Press the HOME key.

Step 2: Press the diamond key and then press F1 to enter the y=editor. Clear any equations in the y=editor by using the arrow keys and pressing the CLEAR key.

Step 3: While you are in the “y1 =” slot, press CATALOG and then press the period “.” (for “W”, which is above the period key). You will immediately be taken to the “when(“ command.

Step 4: Press ENTER to bring the “when(“ command to the “y1 =” slot.

Step 5: While in the “when(“ command, press: x 2nd . 0 , 3 x , x + 5 ) ENTER.
This tells the TI-89 that whenever x is greater than 0, return 3x; whenever x is not greater than 0 (this is the same as whenever x is less than or equal to 0), return x+5

Step 6: Press the diamond key and then press F3 to view the graph of the piecewise function.

Note: If you don’t see your graph, check your window settings. Press the diamond key and then press F2 to access the window.

That’s how to graph piecewise functions on the TI 89 !

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