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Calculus palette: Limit operator

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Context Panel: Evaluate and Display Inline


$\underset{n\to \infty}{lim}\frac{5n4}{2nplus;3}$ = $\frac{{5}}{{2}}$${}$



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Maple's limit operator treats $n$ as a continuous variable. In fact, the Maple developer who maintains the limit command has more than once informed this author that he knows of no algorithm by which a limit can be taken through a discrete variable. In most instances in calculus, this treatment of a discrete index as if it were a continuous variable, does not lead to an erroneous result. But occasionally, a sequence will be encountered where this failure of automatic calculation to provide a limit through the integers will give a misleading result. A simple example is the sequence whose general term is $\mathrm{sin}\left(n\mathrm{pi;}\right){e}^{n}$. Each term of the sequence is zero, so the limit is trivially zero, but Maple will declare the limit of this sequence to be undefined (i.e., does not exist) because the continuous algorithm that is used sees numbers between $1$ and 1 multiplied by larger and larger exponentials.
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Table 8.1.10(a) contains the
task template that, given the general term of a sequence, calculates and graphs its first few members.
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Tools≻Tasks≻Browse: Algebra≻Sequences

Sequences

General term

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$\mathrm{expr}\u2254\frac{5n4}{2nplus;3}$

${\mathrm{expr}}{:=}\frac{{5}{}{n}{}{4}}{{2}{}{n}{\+}{3}}$
 (1) 

Index name


First index value


Last index value


Members

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$\mathrm{seq}\left(\mathrm{expr}\,\=..\right)$

${}\frac{{4}}{{3}}{\,}\frac{{1}}{{5}}{\,}\frac{{6}}{{7}}{\,}\frac{{11}}{{9}}{\,}\frac{{16}}{{11}}{\,}\frac{{21}}{{13}}{\,}\frac{{26}}{{15}}{\,}\frac{{31}}{{17}}{\,}\frac{{36}}{{19}}{\,}\frac{{41}}{{21}}{\,}{2}{\,}\frac{{51}}{{25}}{\,}\frac{{56}}{{27}}$
 (5) 

Graph

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$\mathrm{plot}\left(\left[\mathrm{seq}\left(\left[\,\mathrm{expr}\right]\,\=..\right)\right]\,\mathrm{style}equals;\mathrm{point}comma;\mathrm{symbol}equals;\mathrm{solidcircle}comma;\mathrm{color}equals;\mathrm{red}\right)$





Table 8.1.10(a) The Sequences task template



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Place the cursor somewhere in the cell containing the phrase "General term"and press the Tab key often enough for the cursor to move to, and select the default general term. With this expression autoselected, simply overwrite with the desired general term, most easily obtained by a copy/paste operation. Then, adjust any of the inputs as needed, and simply press the Enter key to execute each command in the template.