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− | <pre> | + | The ''differential variables'' <math>\operatorname{d}x_j</math> are boolean variables of the same basic type as the ordinary variables <math>x_j.\!</math> It is conventional to distinguish the (first order) differential variables with the operative prefix "<math>\operatorname{d}</math>", but this is purely optional. It is their existence in particular relations to the initial variables, not their names, that defines them as differential variables. |
− | It should be noted that the so-called "differential variables" dx_j
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− | are really just the same type of boolean variables as the other x_j.
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− | It is conventional to give the additional variables these inflected | |
− | names, but whatever extra connotations we attach to these syntactic
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− | conveniences are wholly external to their purely algebraic meanings.
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− | In the case of the conjunction f<p, q> = pq, | + | In the example of logical conjunction, <math>f(p, q) = pq,\!</math> the enlargement <math>\operatorname{E}f</math> is formulated as follows: |
− | the enlargement Ef is formulated as follows: | |
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− | Ef<p, q, dp, dq>
| + | {| align="center" cellpadding="6" width="90%" |
− | | + | | |
− | = [p + dp][q + dq]
| + | <math>\begin{array}{l} |
− | | + | \operatorname{E}f(p, q, \operatorname{d}p, \operatorname{d}q) |
− | = (p, dp)(q, dq)
| + | \\[6pt] |
| + | = \quad (p + \operatorname{d}p)(q + \operatorname{d}q) |
| + | \\[6pt] |
| + | = \quad \texttt{(} p, \operatorname{d}p \texttt{)(} q, \operatorname{d}q \texttt{)} |
| + | \end{array}</math> |
| + | |} |
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| + | <pre> |
| Given that this expression uses nothing more than the "boolean ring" | | Given that this expression uses nothing more than the "boolean ring" |
| operations of addition (+) and multiplication (*), it is permissible | | operations of addition (+) and multiplication (*), it is permissible |