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Student Support Forum: 'Re: Plotting x^(1/3)' topicStudent Support Forum > General > Archives > "Re: Plotting x^(1/3)"

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05/20/97 10:28pm

Reply to message #359 from Ben Hawkey: > I just know this has a really
simple answer, but it has been bugging me that I have been unable
to get a real result for -ve values of x. I know they exist, my $50
calculator tells me they exist. and so does my 1st year calc book,
but I'll be damned if I can get Mathematica to give me anything but
complex results. > So if anyone can answer this easy question for
me I'd be very happy :) > > Thanks in advance > Ben Hawkey > ----------------------
In Mathematica, all symbols are considered to be complex. There are
one real and two non-real results for say, -8^(1/3). This can be seen
if you run the command NSolve [x^3 == -8, x]. Since Plot can handle
only real numbers, your plot command will run into trouble unless
you intervene. One possible intervention is to download the RealOnly
package by GeorgeBeck from MathSource. Here is a description: RealOnly:
Two ideas are implemented here. Odd roots of negative numbers are
defined to be negative, and unavoidable complex numbers are signaled
by the symbol Nonreal, in a way similar to the built- in object Indeterminate.
URL: http://www.mathsource.com/cgi-bin/MathSource/Applications/Education/Other/0207-537
If you load this package into your session, your plot will execute
without problems


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