MaplePrimes - answers and comments on Question, solve(exp(-x)-x = 0)???

symbolic vs numeric

Axel Vogt — Wed, 28 May 2008 22:16:48 Z

solve(exp(-x)-x = 0);
evalf(%);
identify(%);

                             LambertW(1)
                             0.5671432904
                             LambertW(1)

tHX aXEL

mikewinifred — Wed, 28 May 2008 22:23:00 Z

thanks axel...im a novice user...some ques will be silly..kindly excuse me.

stumbling is quite natural - some crutches are helpful

Axel Vogt — Wed, 28 May 2008 23:24:06 Z

Stumbling is quite natural ... Acer said it quite (anyway I am aware
of my ocassional unpatientience ...)

The question is not silly. To some extend it is ok get a feeling for
the CAS by hands-on and ignoring the example sheets, help or guides.
I understand that quite well, I hated lectures a bit :-)

But from own experience: at least try to follow some systematics, you
will have a better feeling by looking at you learning curve.

So either look what comes with Maple (no, just do it, look at what you
already have and what sounds to interest you) and least work through
the Introductory Programming Guide (ignoring stuff on GUI first) and
the table of contents of Advanced Programming Guide (to have in mind
wher to look things up), both are available for download as pdf.


Besides Maple's application center there are some good (but may older)
lectures on the web. Due to copy rights I do not want to load up such
stuff, but Google may help you, here are some (free for download):


Kraft + "Maple For Math Majors"
Clark + "Symbolic Computations in Mathematics"
Kolinsky + "Einführung in das Computeralgebrasystem Maple"
Geddes + "Symbolic and Numeric Scientific Computation in Maple"

exact vs approximate

acer — Wed, 28 May 2008 22:23:58 Z

What Axel's trying to show is that LambertW(1) is an exact symbolic representation of the value that satisfies the equation.

The 0.56.. floating-point result is only an approximation accurate to a finite number of digits. The evalf() command can be used to approximate the exact symbolic quantity to however many decimal digits you wish.

You could also use fsolve instead of solve, if you wanted only the floating-point result.

Maple is a computer algebra system (CAS) and it is able to do lots of exact computation involving such exact symbolic quantities, which is why `solve` doesn't just return the approximate result.

acer