Using ZOOM in Sequence Mode on the TI-83 Plus

By C. C. Edwards

Pressing [ZOOM] accesses the Zoom menu on the TI-83 Plus graphing calculator. On this menu you see all the Zoom commands that are available for graphing functions. Not all of them are useful when graphing sequences, however.

  • ZoomFit: This command finds a viewing window for a specified portion of the sequence.

  • Zbox: After the graph is drawn, this command allows you to define a new viewing window for a portion of your graph by enclosing it in a box. The box becomes the new viewing window. To construct the box:

    1. Press [ZOOM][1].

    2. Define a corner of the box.

      To do so, use the

      Right, left, up, and down keys on the TI-83 Plus calculator

      keys to move the cursor to the spot where you want one corner of the box to be located, and then press [ENTER]. The calculator marks that corner of the box with a small square.

    3. Construct the box.

      To do so, press the

      The four arrow keys on a graphing calculator.

      keys. As you press these keys, the calculator draws the sides of the box.

      When you use ZBox, if you don’t like the size of the box, you can use any of the

      The TI-83's four arrow keys

      keys to resize the box. If you don’t like the location of the corner you anchored in Step 2, press [CLEAR] and start over with Step 1.

    4. When you’re finished drawing the box, press [ENTER] and the graph will be redrawn in the viewing window specified by the box.

      A graph redrawn in the viewing window specified by the box.

      When you use Zbox, Õ is pressed only two times. The first time you press it is to anchor a corner of the zoom box. The next time you press Õ is when you’re finished drawing the box and are ready to have the calculator redraw the graph.

  • Zoom In and Zoom Out: After the graph is drawn, these commands allow you to zoom in on a portion of the graph or to zoom out from the graph. They work very much like a zoom lens on a camera. To use these commands:

    1. Press [ZOOM][2] if you want to zoom in, or press [ZOOM][3] if you want to zoom out.

    2. Use the

      The direction arrows on a TI-83 Plus

      keys to move the cursor to the spot on-screen from which you want to zoom in or zoom out.

      This spot becomes the center of the new viewing window.

    3. Press [ENTER].

      You can press [ENTER] again to zoom in closer or to zoom out one more time.

    4. Press [CLEAR] when you’re finished zooming in or zooming out.

If you used a Zoom command to redraw a graph and then want to undo what that command did to the graph, press

The Zoom, right arrow, and 1 keys.

to select ZPrevious from the Zoom Memory menu. The graph is then redrawn as it appeared in the previous viewing window.