Here, in question and answer form, are some situations that might arise when you are working in a document.
Q. My screen has gotten cluttered with lines or marks that don't belong there (or I can't see something on the screen that I know is there). What can I do?
A. PressESCor choose View + Refresh to refresh your screen.
Q. What can I do if I type an expression in text mode that I meant to have in mathematics mode?
A. Select the expression with the mouse or select the expression from the keyboard by placing the insertion point to the left of the expression and pressingSHIFT+RIGHT ARROW. Then click the Toggle Text/Math button to change it to . Q. What can I do if I cannot see all of my work on the screen either horizontally or
vertically?
A. If a piece of mathematics extends beyond the width of the screen, you can scroll horizontally using the scroll bars at the bottom of the screen. If the mathematics has possible breaking points, add an Allow Break at appropriate places from the Insert + Spacing + Break menu. To see more of your document on the screen at a time, you can reduce the size of the screen font. Click View and choose Working. Change the percentage in the Working View box and choose OK. The 1x on the View menu gives 100% and the 2x gives 200%. The range for Working View is 50% (very small) to 400% (huge).
Q. Can I change the behavior of theSPACEBAR,ENTER, andTABkeys?
A. A setting on the Edit page of Tools + User Setup will allow you to change these behaviors. The default behavior allows you to enter multiple spaces, horizontal or vertical, by pressing SPACEBAR, ENTER, orTAB. Follow directions on the menu to change spacing behaviors. For a variety of spacing options, choose Insert + Spacing + Horizontal Space or Vertical Space, and choose an appropriate size space. If you check Custom Space, you can specify the width or height of the space or choose stretchy spaces. Mathematics is automatically spaced appropriately for most situations. To keep a mathematical expression meaningful for computation, be sure any added space stays in mathematics mode.
Q. I tried a computation and nothing happened (although my system does carry out other computations). How can I nd out what I did wrong?
A. One common problem is a forgotten de nition. Choose Compute + De nitions + Show De nitions and look for a de nition that is interfering with your computation.
Apply Compute + De nitions + Unde ne to the variable or function that is causing the problem. If this does not solve the problem, click Tools, choose Engine Setup, Error Handling page, and change the setting for Error Noti cation. With a setting of None, you get no response to errors. With a setting of Beep, you get a warning sound with an error. With other settings, you get messages with information about the error—usually the error message generated by the computing engine. (See page 15 for more detailed information about error handling.)
Q. I tried to take the absolute value of an expression and nothing happened. What is wrong?
A. The symbols for absolute value are the vertical lines from the dialog box under Brackets . (The keyboard vertical line will also work, but expanding brackets are less vulnerable to misinterpretation.) Perhaps you used the vertical lines from the symbol panel under the Binary Relations button . Although they appear similar, they are not the same symbols and will not be interpreted as absolute-value symbols.
Q. How can I be sure exactly how my mathematical expression is being interpreted?
A. Select the expression and pressCTRL+ ? or choose COMPUTE+ INTERPRET. The expression will be presented in an unambiguous form. For example,
sin a= sin b = sin a
Add parentheses or change the expression some other way to remove an ambiguity.
Q. The mathematics I entered is being misinterpreted but it looks okay on the screen.
What should I change?
A. Is your expression in a display? If you place the insertion point in a display and choose Evaluate, the entire contents of the displayed object will be evaluated, even if part of it is text. To avoid this type of behavior, select the expression or equation with click and drag before choosing a command. If you are using braces, square brackets,
or non-expanding parentheses in place of expanding parentheses, try changing all of these to expanding parentheses. It is advisable, as a general rule, to use expanding parentheses whenever parentheses are called for. For a variety of reasons, other choices for brackets are vulnerable to misinterpretation—particularly if the left and right parentheses do not match. Example: (2)(3) is entered with the outer ses “()” expanding brackets and the inner parentheses “)(” non-expanding parenthe-ses. Evaluating this non-matched expression gives (2)(3) = 2, which is probably not what is intended! Although the expanding brackets under the Brackets button , the expanding brackets and , and non-expanding brackets from the keyboard are generally interchangeable (when properly matched), there are a few circumstances in which the square brackets or keyboard brackets or even keyboard parentheses do not work properly. In particular, the less-than and greater-than sym-bols on the keyboard should not be used as brackets. These two symsym-bols, as well as the symbols on the panel under , are binary relations and generally will not be interpreted as brackets. Square brackets and braces have some special meanings for the computing engine, and even though the interface is designed to accept as many ordinary mathematics expressions as possible, the use of nonexpanding or unusual brackets can lead to misinterpretations.
Q. My expression will not plot. What can I try?
A. Choose Compute + De nitions + Show De nitions, or click the Show De ni-tions button on the Compute toolbar, and look to see if any of the variables you are using are de ned. If so, select the variable and choose Compute + De ni-tions + Unde ne. If a forgotten de nition is not the problem, hold down theCTRL
key while giving the plot command. This will cause the Plot Properties dialog to come up before the system makes the plot. Choose the Items Plotted page and try changing the settings for Variables and Intervals and/or uncheck the Adjust Plot for Discontinuities option.
Q. My document contains complicated plots, and scrolling through the document is very slow. Can I turn off the plots temporarily to save myself time as I edit the le?
A. You can turn off the computing engine temporarily: choose Tools + Computation Setup, go to the Engine Selection page, and choose None. If you want to keep the computing engine active, you can set the plot either to appear on the screen as an icon or as an empty frame: select the plot, choose Edit + Properties, and on the Layout page, under Screen Display Attributes, check Iconi ed or check Frame Only. If you choose Iconi ed, you can enter a Name for the icon on the Labeling page of the Plot Properties dialog. Or, if your plots are in nal form, you can rename the plot snapshots and import them as pictures that take much less time to load. See page 225 for details on this option.