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The briefest expression for logical truth is the empty word, usually denoted by <math>\varepsilon\!</math> or <math>\lambda\!</math> in formal languages, where it forms the identity element for concatenation. To make it visible in this text, I denote it by the equivalent expression "<math>((~))\!</math>", or, especially if operating in an algebraic context, by a simple "<math>1\!</math>". Also when working in an algebraic mode, I use the plus sign "<math>+\!</math>" for exclusive disjunction. Thus, we may express the following paraphrases of algebraic forms:
The briefest expression for logical truth is the empty word, usually denoted by <math>\varepsilon\!</math> or <math>\lambda\!</math> in formal languages, where it forms the identity element for concatenation. To make it visible in this text, I denote it by the equivalent expression "<math>((~))\!</math>", or, especially if operating in an algebraic context, by a simple "<math>1\!</math>". Also when working in an algebraic mode, I use the plus sign "<math>+\!</math>" for exclusive disjunction. Thus, we may express the following paraphrases of algebraic forms:
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:{| cellpadding="4"
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<center>
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| ''A'' + ''B''
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<p><math>\begin{matrix}
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| =
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x + y & = & (x, y)
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| (''A'', ''B'')
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\end{matrix}</math></p>
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|-
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| ''A'' + ''B'' + ''C''
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| =
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| ((''A'', ''B''), ''C'')
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| =
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| (''A'', (''B'', ''C''))
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|}
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One should be careful to observe that these last two expressions are not equivalent to the form (''A'', ''B'', ''C'').
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<p><math>\begin{matrix}
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x + y + z & = & ((x, y), z) & = & (x, (y, z))
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\end{matrix}</math></p>
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</center>
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It is important to note that the last expressions are not equivalent to the triple bracket expression <math>(x, y, z).\!</math>
<font face="courier new">
<font face="courier new">