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If $R$ is transitive relation. How can I prove that composition of its transpose is also transitive.

i.e. $R^T\ ;R^T$ is transitive too.

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  • $\begingroup$ What is the transposition of a relation? $\endgroup$
    – Git Gud
    Oct 30 '15 at 16:22
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    $\begingroup$ @GitGud the matrix of a relation is its adjacency matrix. That is, the matrix of a relation on $n$ elements is an $n \times n$ matrix whose $a=i,j$ entry is a $1$ if $(x_i,x_j) \in R$ and $0$ otherwise. The transpose relation is the relation corresponding to the transposed graph. $\endgroup$ Oct 30 '15 at 16:25
  • $\begingroup$ More concisely: $xRy \iff y R^Tx$ $\endgroup$ Oct 30 '15 at 16:26
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Let $x R^T y$ and $ y R^T z$. Then $ zRy $ and $ yRx$ by definition of the transpose relation. Since $R$ is transitive, that means that $zRx$. Again, by definition of the transpose relation, $xR^Tz$.

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  • $\begingroup$ Thank you for your answer! $\endgroup$
    – TechJ
    Oct 30 '15 at 16:47

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