Using the Scratchpad
The Scratchpad is a feature of the TI-Nspire™ handheld that lets you quickly:
• Evaluate math expressions.
• Graph functions.
Opening and closing the Scratchpad
` From the Home screen, press
»
to open the Scratchpad.
The first time you open the Scratchpad, a blank page opens with the
Calculator active.
` Press
»
to alternate between the Calculate and Graph pages.
Using the Scratchpad 383
` Press b
to see the Scratchpad Calculate or Scratchpad Graph menu. These menus are subsets of the TI-Nspire™ menus for the
Calculator and Graphs & Geometry applications. For complete listings of those menus, refer to the documentation for those applications.
` Press d
to close the Scratchpad.
Calculating with the Scratchpad
From the Scratchpad Calculate page, enter a math expression on the entry line, then press
·
to evaluate the expression. Expressions display in standard mathematical notation as you enter them.
Each evaluated expression and result becomes part of the Scratchpad history, displayed above the entry line.
Entering simple math expressions
Note: To enter a negative number, press v
and then enter the number.
Suppose you want to evaluate
1. Select the entry line in the work area.
2. Type
2
l
8
to begin the expression.
3. Press
¢
to return the cursor to the baseline, and then complete the expression by typing: r
43
p
12
4. Press
·
to evaluate the expression.
The expression displays in standard mathematical notation, and the result displays on the right side of the page.
Note: You can force a decimal approximation in a result by pressing
/ ·
instead of
·
.
384 Using the Scratchpad
Pressing
/ ·
forces the approximate result.
Note: Results formatting can also be adjusted in Settings. See Working with documents on the TI-Nspire™ handheld for more information about
Settings.
Inserting items from the Catalog
You can use the Catalog to insert functions and commands, units, symbols, and expression templates into the entry line.
1. Press k
to open the Catalog. By default, the first tab is displayed, which lists all commands and functions in alphabetical order.
Catalog for a non-
CAS handheld
Catalog for a CAS handheld
Using the Scratchpad 385
2. If the function you are inserting is visible in the list, select it and press
·
to insert it.
3. If the function is not visible: a) Press a letter key to jump to the entries that begin with that letter.
b) Press
¤
or
£ as necessary to highlight the item you are inserting.
c) Click a numbered tab to list functions by category: math functions, symbols, math templates, library objects, and value for standard measurement units (CAS).
d) Press
·
to insert the item into the entry line.
Using an expression template
Templates help you enter matrices, piecewise functions, systems of equations, integrals, derivatives, products, and other math expressions.
For example, suppose you want to evaluate
1. Press t
to open the Template palette.
2. Select to insert the algebraic sum template.
The template appears on the entry line with small blocks representing elements that you can enter. A cursor appears next to one of the elements to show that you can type a value for that element.
3. Use the arrow keys to move the cursor to each element’s position, and type a value or expression for each element.
4. Press
·
to evaluate the expression.
386 Using the Scratchpad
Inserting expressions using a wizard
You can use a wizard to simplify entering some expressions. The wizard contains labeled boxes to help you enter the arguments in the expression.
For example, suppose you want to fit a y=mx+b linear regression model to the following two lists:
{1,2,3,4,5}
{5,8,11,14,17}
1. Press k 1
to open the Catalog and show the alphabetic list of functions.
2. Click inside the list, and then press
L
to jump to the entries that begin with “L.”
3. Press
¤
as necessary to highlight
LinRegMx
.
4. If the
Wizards On
option is not checked: Press e e
to highlight
Wizards On
, press
·
to change the setting, then press e e
to highlight
LinRegMx
again.
LinRegMx function in a non-CAS handheld
Using the Scratchpad 387
LinRegMx function in a
CAS handheld
5. Press
·
.
A wizard opens, giving you a labeled box to type each argument.
6. Type {
1,2,3,4,5
} as
X List
.
7. Press e
to move to the
Y List
box.
8. Type
{5,8,11,14,17}
as
Y List
.
9. If you want to store the regression equation in a specific variable, press e
, and then replace
Save RegEqn To
with the name of the variable.
10. Select
OK
to close the wizard and insert the expression into the entry line.
The expression is inserted along with statements to copy the regression equation and display the variable
stat.results, which will contain the results.
388 Using the Scratchpad
LinRegMx {1,2,3,4,5},{5,8,11,14,17},1: CopyVar stat.RegEqn,f1: stat.results
The Scratchpad then displays the
stat.results variables.
Note: You can copy values from the
stat.results variables and paste them into the entry line.
Viewing the history
Each evaluated expression and result becomes part of the Scratchpad history, displayed above the entry line.
` Press
£
or
¤
to scroll through the history.
À
Current entry/total entries
À
Using the Scratchpad 389
Copying a history item to the entry line
You can quickly copy an expression, subexpression, or result from the history into the entry line.
1. Press
£
or
¤
to move through the history and select the item that you want to copy.
2. Optionally, select part of the expression or result by using
Shift
in combination with the arrow keys.
3. Press
·
to copy the selection and insert it into the entry line.
Clearing the history
When you clear the history, all variables and functions defined in the history retain their current values. If you clear the history by mistake, use the undo feature.
` From the
Actions
menu, select
Clear History
.
(Press b 1 5
.)
All expressions and results are removed from the history.
Editing Scratchpad expressions
Although you cannot edit a Scratchpad Calculate expression in the history, you can copy all or part of an expression from the history and paste it to the entry line. You can then edit the entry line.
Inserting elements into the entry line
1. Press e
,
¡
,
¢
,
£
, or
¤
to position the cursor in the expression. The cursor moves to the closest valid position in the direction that you press.
2. Type the elements or insert them from the Catalog.
Selecting part of an expression
You can delete, cut, or copy a selected part of an expression.
390 Using the Scratchpad
1. Press
¡
,
¢
,
£
, or
¤
to move the cursor to a starting point in the expression.
2. Press and hold g
and press
¡
,
¢
,
£
, or
¤
to select.
– To delete the selection, press
.
.
– To cut the selection to the Clipboard, press
/ X
.
– To copy the selection to the Clipboard, press
/ C
.
– To paste the selection to a new entry line in Scratchpad, press
/ V
.
Graphing with the Scratchpad
From the Scratchpad Graph page, click the Entry Line Expand button to display the entry line and type an expression to graph. The entry line displays the required format for typing a function. The default graph type is Function, so the form f1(x)= displays.
1. Choose
Graph Type
from the menu, and select a graph type.
For example,
• To graph a scatter plot, press b 3 4
. Click var to choose variable to plot as x and y for sn.
• To graph a function, press b 3 1
.
The entry line changes to display the expression format for the specified graph type. You can specify multiple functions of each graph type.
2. Type an expression and any other parameters required for the graph type.
3. Press
·
to graph the function, or press
¤
to add another function.
If necessary, you can use press b 4
to choose a tool on the
Window/Zoom
menu and adjust the viewing area.
When you graph the expression, the entry line disappears to show an uncluttered view of the graph. If you select or trace a function, that function displays on the entry line. You can change a function by editing its expression or grabbing and changing the graph.
Using the Scratchpad 391
As you graph multiple functions on the axes, the label containing the expression displays for each. You can define and graph a maximum of
99 functions of each type.
4. Use the b
key to explore and analyze the graphed function by tracing it, finding points of interest, or assigning a variable in the expression to a slider.
Viewing the function table
` To display a table of values for the current function, press b 2 5
.
` To hide the function table, click the graph and then press b 2 5
.
Changing the appearance of the axes
As you work with graphs, the Cartesian axes are displayed by default.
You can change the appearance of the axes in the following ways:
1. Press b 4
and choose the Zoom tool to use.
2. Select the axes and press
/ b 3
to activate the
Attributes
tool.
a) Press 9 or : to move to the attribute to change. For example, choose the end style attribute.
b) Press
7 or 8 to choose the style to apply. c) Change any other attributes of the axes as required for your work, then press d
to exit the attributes tool.
3. Adjust the axes scale and tic mark spacing manually.
392 Using the Scratchpad
a) Click and hold one tick mark, and move it on the axis. The spacing and number of tic marks increases (or decreases) on both axes.
b) To adjust the scale and tic mark spacing on a single axis, press and hold g
, and then grab and drag a tic mark on that axis.
4. Change axis end values by double-clicking them and typing new values.
5. Adjust the location of the axes. To move the existing axes without resizing or rescaling them, click in and drag an empty region of the screen until the axes are in the desired location.
6. Change the axes’ scales by pressing b 4 1
.
Type the values of your choice over the current values for x-min, x-max, y-min, and y-max and click
OK
.
7. Press b 2 1
to hide or show the axes.
• If the axes are shown on the page, selecting this tool hides them.
• If the axes are hidden on the page, selecting this tool redisplays them.
Tracing a graphed function
Graph Trace moves through the points of a graphed function, parametric, polar, sequence, or scatter plot. To enable the trace tool:
1. Press b 5 1 to move across the points in a graphed function in Trace model.
2. (Optional) To change the step increment for tracing, press b 5 3
.
Using the Scratchpad 393
After you type a different step increment, the Graph Trace tool moves across the graph in steps of that size, instead of moving at the default step automatically defined with a function.
3. Use Graph Trace to explore a graphed function in the following ways:
• Move to a point and hover to move the trace cursor to that point.
• Press 7 or 8 to move from point to point on the function’s graph.
The coordinates of each point traced displays.
• Press 9 or : to move from one function’s graph to another, or to a scatter plot. The point’s coordinates update to reflect the new location of the trace. The trace cursor is positioned on the point of the new graph or plot with the closest x value to the last point identified on the previously traced function or graph. You can trace multiple functions as described in Tracing all graphs.
• Type a number and press
·
to move the trace cursor to that value on the function’s graph.
• Create a persistent point that remains on the graph while in
Graph Trace mode by pressing
·
when the trace point reaches the point you want to label.
• Trace through and identify the points at which the function has no defined x or y value (a discontinuity). The string undef displays instead of a value when you move over a point that is not defined for the function.
Notes:
• When you select or trace a function on the work area, that function displays on the Edit Line.
• When you trace beyond the initially visible graph, the screen pans to show the area being traced.
4. Exit Graph Trace by pressing d
or by choosing another tool.
Finding points of interest
You can use the tools on the
Analyze Graph
menu to find a point of interest in a specified range of any graphed function. Choose a tool to find zero, the minimum or maximum, the point of intersection or inflection, or the numeric derivative (dy/dx) or Integral on the graph.
1. Select the point of interest that you want to find on the
Analyze
Graph
menu. For example, to find a zero, press b 6 1
.
394 Using the Scratchpad
The icon for the selected tool displays at the top left on the work area. Point to the icon to view a tooltip about how to use the selected tool.
2. Click the graph you want to search for the point of interest, then click a second time to indicate where to start the search for the point.
The second click marks the lower bound of the search region and a dotted line displays.
Note: If you are finding the derivative (dy/dx), click the graph at the point (numeric value) to use for finding the derivative.
3. Press
3 or 4 to move the dotted line that marks the search region, then click the point at which you want to stop the search (upper bound of the search region).
4. Press
·
at the point to start the search. The tool shades the range.
If the search region you specified includes the point of interest, a label for the point displays. If you change a graph that has points of interest identified, be sure to check for changes in points of interest.
For example, if you edit the function on the entry line or manipulate a plot, the point where the graph intersects zero can change.
The labeled points of interest remain visible on the graph. You can exit the tool by pressing d
or choosing another tool.
Working with variables in the Scratchpad
Scratchpad variables are shared between Scratchpad Calculate and
Scratchpad Graph, but not with any TI-Nspire™ documents. If you use the same name for a Scratchpad variable and a variable in a document, no conflict occurs unless you attempt to copy expressions between documents and the Scratchpad.
Using the Scratchpad 395
Saving the Scratchpad contents
You can save the Scratchpad Calculate page, the Scratchpad Graph page, or both as a TI-Nspire™ document.
1. Press
~
, then select
Save to Document
.
2. Press
·
.
The Save to Document dialog box opens.
3. Select the page or pages to save.
4. If a document is open, select either New or Current document.
5. Click
Save
.
• If you selected to save to an open document, the Scratchpad pages are added to the document.
• If you selected to save to a new document:
– Click
Yes
when the Save dialog box opens.
– Type a name for the document.
– Click
Save
to save the new document.
Clearing Scratchpad contents
Complete the following steps to delete the calculations and graphing work from the Scratchpad application.
1. Press
~
, then select
Clear Scratchpad
.
2. Press
·
to delete the Scratchpad contents.
396 Using the Scratchpad
