Example 1
In the following example, it is unclear whether the argument $i$represents the summand or the index.
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$\mathrm{sum}\left(i\right)$

Solution:
For this example, we assume the intention was for the summand and index to both be $i\.$ You must explicitly state both arguments for sum.
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$\mathrm{sum}\left(i\,i\right)$

$\frac{{1}}{{2}}{}{{i}}^{{2}}{}\frac{{1}}{{2}}{}{i}$
 (3.1) 
Example 2
In the following example, attempting to sum more than one summand at a time results in an error.
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$\mathrm{sum}\left({i}^{2}\,i\,i\right)$

Solution:
To sum more than one summand at at time, use the map command.
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$\mathrm{map}\left(\mathrm{sum}\,\left[{i}^{2}\,i\right]\,i\right)$

$\left[\frac{{1}}{{3}}{}{{i}}^{{3}}{}\frac{{1}}{{2}}{}{{i}}^{{2}}{\+}\frac{{1}}{{6}}{}{i}{\,}\frac{{1}}{{2}}{}{{i}}^{{2}}{}\frac{{1}}{{2}}{}{i}\right]$
 (3.2) 
Example 3
In the following example, attempting to calculate the sum of $i\+j$over both index variables results in an error. This statement is not welldefined.
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$\mathrm{sum}\left(i\+j\,i\=1..3\,j\=6..8\right)$

Solution:
Depending on the interpretation, one possible solution is to express the sum in the following manner: if the indices are meant to be sequenced individually, then the following statement corrects the error and produces the intended result.
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$\mathrm{sum}\left(\mathrm{sum}\left(i\+j\,i\=1..3\right)\,j\=6..8\right)$

Otherwise, if the indices are meant to be sequenced in tandem, then the following statement corrects the error and produces the intended result.
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$\mathrm{sum}\left(\mathrm{eval}\left(i\+j\,j\=i\+5\right)\,i\=1..3\right)$
