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The following list are questions commonly asked by new users of DERIVE. Also provided is the section number where more detailed information can be found in the user manual.
All versions of DERIVE starting with version 1.0 are "Year 2000 compliant". The product currently being shipped is DERIVE for DOS (DfD) 4.0x.
DfD 4.0x does not record, store, manipulate, or display dates. It relies on the MS-DOS file system to accurately timestamp files created with DfD.
In summary, DERIVE is dependent on Microsoft products which are designed to support dates well into the next century.
Q: If I decide not to issue a command, how do I abort the command and escape from the submenu?
A: Press the Esc key until you return to the top-level command menu (see Section 2.3 in the user manual).
Q: While line editing, how do I insert characters in a line without over-writing the characters that are already there?
A: Press the Ins key to switch to insert mode. The abbreviation Ins will appear on the status line on the bottom of the screen (see Section 2.4 in the user manual).
Q: Why does DERIVE periodically pause in the display of expressions and plots?
A: When DERIVE runs out of memory, it recycles memory occupied by data structures that are no longer needed. During the time it takes for this recycling, other processing stops. On PC compatible computers, a full-block cursor is displayed on the first character of the message line (see Section 2.2 in the user manual) during this process.
Q: Why doesn't the percentage of free space displayed on the status line change as soon as I generate or remove expressions?
A: This percentage is not updated until DERIVE recycles memory (see Section 2.2 in the user manual).
Q: How do I get a summary of the current system control settings?
A: Use the Help System command to display the current setting of all the system control variables (see Sections 2.5 and 2.14 in the user manual).
Q: How do I display a DOS file directory from within DERIVE ?
A: Issue the Options Execute command and then enter DIR/W at the DOS prompt (see Section 2.7 in the user manual). Also, after issuing a Transfer Load command, you can press F1 to display and choose a file from a DOS directory (see Section 2.9 in the user manual).
Q: Why do the direction keys sometimes stop working?
A: You probably pressed the NumLock key. Press it again to toggle it off.
Q: How do I access the elements of a vector or matrix?
A: Use the arrow keys to highlight the desired element, and press the F3 or F4 function key to insert the element on the author line (see Section 3.3 in the user manual). A highlighted vector or matrix element can also be used as an operand of the Build command (see Section 3.5 in the user manual). The SUB operator or the ELEMENT function can also be used to extract elements (see Section 8.3 in the user manual).
Q: Why doesn't LN(e) simplify to 1?
A: In DERIVE, e is a simple variable, not the base of the natural logarithms (2.71828...). The base of the natural logarithms is displayed as ê and it is entered by typing #e or by pressing Alt-E on PC compatible computers (see Section 6.1 in the user manual).
Q: Why doesn't i² simplify to -1?
A: In DERIVE, i is a simple variable, not the imaginary unit, SQRT(-1). The imaginary unit is displayed as î and it is entered by typing #i or by pressing Alt-I on PC compatible computers (see Section 6.8 in the user manual).
Q: How do I turn the name of a function I defined back into a variable name?
A: Use the Declare Variable command to declare the name a real-valued variable (see Section 4.10 in the user manual).
Q: Why doesn't DERIVE simplify LN(x²-x) - LN(x) to LN(x-1)?
A: This transformation is invalid if x is negative. However, if you use the Declare Variable command to declare that x is nonnegative, DERIVE will simplify the expression. In general, DERIVE will not use a transformation unless it can determine that the transformation is valid (see Section 4.10 in the user manual).
Q: When I use square brackets when entering expressions like 3 [x+y], why does the result not behave correctly?
A: In DERIVE, square brackets are used exclusively for entering vectors and matrices (see Section 8.1 in the user manual). Thus the above expression is interpreted as 3 times the one element vector [x+y]. Parentheses rather than brackets should be used to control the order in which operators are applied (see Section 3.1 in the user manual). Note that DERIVE has to display multi-line parentheses using square brackets, because large parentheses are not part of the extended ASCII character set.
Q: When I integrate the derivative of x/(x+1), why do I get -1/(x+1) instead of the original expression?
A: Antiderivatives are not unique and may differ by a constant. In this case x/(x+1) and -1/(x+1) differ by 1, and both are valid antiderivatives.
Q: How can I adjust the aspect ratio used for 2D plots?
A: Use the aXes command and adjust the Rows and Columns fields (see Section 5.1.2 in the user manual).
Q: For 2D plots, how do I change the region being plotted?
A: Use the Range command. Alternatively, you can move the cross near the desired center of the plot, zoom in or out as desired, and then issue a Center command (see Section 5.1.3 in the user manual).
Q: How do I make a 2D plot of a function implicitly defined by an equation such as x²+y²=1?
A: Highlight the equation and plot it in a 2D-plot window just as you would an explicitly defined function (see Section 5.1.9 in the user manual).
Q: Why can't I plot x ^(1/3) for negative x ?
A: The principal cube root of a negative number is complex and cannot be plotted directly. Use the Manage Branch command to make DERIVE select the real branch instead of the principal branch (see Section 4.5 in the user manual).
Q: When I try to plot a vector of two expressions, why doesn't DERIVE plot them correctly?
A: DERIVE plots a vector of two univariate expressions parametrically (see Section 5.1.7 in the user manual). However, you can add ? as a dummy third element to the vector so DERIVE produces the multiple plot you desire.
Q: My computer has a Hercules compatible graphics card. Why don't I get Hercules graphics when I select it using the Options Display command?
A: Run the HERCULES.COM resident program before starting DERIVE (see Section 2.12 in the user manual).
Q: When I switch to graphics display mode, why are strange characters displayed on the screen for integral signs, built-up fractions, Greek letters, and the borders of the window?
A: To display characters in the extended ASCII character set in graphics mode, some computers (e.g. the AT&T 6300 and the Toshiba 3100) require that a graphics table be loaded into memory before starting DERIVE. The program to load the table may be called GRAFTABL.COM or GFTABLE.COM (see your computer manual for details). If no such program is available, use the Options Display command and select the standard character set (see Section 2.12 in the user manual).
Q: Why is my 3D plot just a coarse collection of dots?
A: For a higher resolution plot, switch from text to a graphics display mode (see Section 2.12 in the user manual).
Q: How can I make a 3D plot of two intersecting surfaces?
A: You can't. However, plotting the minimum of the two surfaces allows you to see their curve of intersection. For example, try plotting MIN(x²+y², 15).
Q: What can I do if a Memory Full warning message appears while plotting in 3D?
A: Reduce the number of grid lines (see Section 5.2.1 in the user manual), close unneeded windows (see Section 2.13 in the user manual), and/or remove expressions from the algebra window (see Section 3.7 in the user manual).
Q: How do I reset all the plot window parameters to their default values?
A: Use the Window Designate command to replace the current 3D-plot window with a new one (see Section 2.13 in the user manual).
Q: How do I print the mathematical expressions in an algebra window?
A: Use the Transfer Print Expressions Printer command (see Section 2.10 in the user manual). Naturally your printer must be on line and correctly connected to your computer (see your DOS and printer manuals for details).
Q: Why aren't mathematical expressions printed using integral signs and Greek letters?
A: If your printer is capable of printing the extended ASCII character set, use the Transfer Print Expressions Options command and select the Extended character set (see Section 2.10 in the user manual).
Q: Why don't I get a good printout when I use the Transfer Print Screen Printer command or press Shift-F10 to print an image of the DERIVE screen?
A: Before printing, use the Transfer Print Options command to select the proper printer type (Laserjet, Dotmatrix, or color Deskjet), and use the Options Display command to select a graphics display mode (see Section 2.12 in the user manual).
Q: How can I incorporate an image of a DERIVE screen into a manuscript?
A: Most popular word processors can import graphics images in the form of TIF (Tagged Image Format) files (see your word processor manual for details). Use the Transfer Print Screen File command or press Ctrl-F10 to save an image of the current DERIVE screen as a TIF file (see Section 2.11 in the user manual). To save a screen image, first use the Options Display command to switch to graphics mode (see Section 2.12 in the user manual).
A: Currently Soft Warehouse, Inc. has no plans to implement DERIVE on platforms other than DOS and Windows based computers. Such project whould require considerable time and effort. Instead we will continue to devote 100% of our resources to making improvements and extensions to DERIVE for DOS.
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Revised 03/09/98 1:03 PM
DERIVE is a registered trademark of Soft Warehouse, Inc.
All contents copyright (c) 1995-98
SOFT WAREHOUSE, INC.
This document has been printed from Chartwell-Yorke Website at http://www.chartwellyorke.com
