The window and zoom

9.1Set the viewing window#

The graph screen shows a rectangle of the plane. WINDOW sets its edges: Xmin and Xmax (left and right), Ymin and Ymax (bottom and top), the tick spacing Xscl and Yscl, and Xres (how many pixels apart points are plotted; 1 is the finest). The standard window is −10 to 10 on both axes.

Move between fields with ▼ and ▲. Type a new number to replace a value (an expression such as −2π also works), then press enter.

Example 9.1

Change Xmax

1. In WINDOW move down once to Xmax, type 5 and press enter.

   window▼5enter▲

Example 9.2

Type an expression in a field

1. Type −2π in Xmin and press enter, then move up.

   window(−)22ndπ^enter▲

Example 9.3

A window that cannot be drawn

1. Set Xmin to 20, which is bigger than Xmax, then press graph.

   window20entergraph

9.2The ZOOM menu#

Press zoom. Choose an item with its number, or press ▶ for the MEMORY tab.

MEMORY tab: 1 ZPrevious goes back to the window before the last zoom, 2 ZoomSto saves the current window, 3 ZoomRcl restores the saved one.

Example 9.4

ZDecimal

1. Press zoom then 4, then open WINDOW to read the values.

   zoom4window

Example 9.5

ZInteger

1. Press zoom then 8, then WINDOW.

   zoom8window

Example 9.6

ZTrig

1. Press zoom then 7, then WINDOW.

   zoom7window

Example 9.7

Go back with ZPrevious

1. Zoom to ZDecimal.

   zoom4

2. Press zoom, right, 1 (ZPrevious), then open WINDOW. The old Xmax of 10 is back.

   zoom▶1window

Example 9.8

Save and restore a window

1. Zoom to ZDecimal and save it with zoom, right, 2 (ZoomSto).

   zoom4zoom▶2

2. Zoom to ZStandard, then restore with zoom, right, 3 (ZoomRcl) and open WINDOW.

   zoom6zoom▶3window

Example 9.9

ZoomFit

1. Graph Y1 = X² and press zoom 0. The Y range is chosen to fit the curve.

   y=X,T,θ,nx²▼zoom0window

9.3Zoom in, zoom out and draw a zoom box#

Zoom In and Zoom Out first show the graph with a free cursor. Move the cursor to the centre you want and press enter; the window is rescaled by a factor of 4 about that point. Press enter again to zoom further. For ZBox, press enter at one corner, move the cursor to the opposite corner and press enter again.

Example 9.10

Zoom in about the origin

1. Press zoom, 2 and enter, then open WINDOW.

   zoom2enterwindow

Example 9.11

Zoom out about the origin

1. Press zoom, 3 and enter, then open WINDOW.

   zoom3enterwindow

Example 9.12

Draw a zoom box

1. Press zoom, 1 (ZBox) and enter at the starting corner.

   zoom1enter

   

2. Move the cursor 66 steps right and 41 steps up, then press enter.

   ▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▶▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲enterwindow

9.4Move the free cursor on a graph#

On a graph screen the arrow keys move a free cursor one pixel at a time and the bottom line shows its coordinates (if CoordOn is set in FORMAT). The pixel width on screen is $\Delta X=\dfrac{X_{max}-X_{min}}{264}$.

Example 9.13

Read the coordinates under the cursor

1. Press graph then right once.

   graph▶