If R and S are relatives from A to B, then which of the following statements are false?
(i) If R ≤ S, then \( S^{-1}\leq R^{-1} \)
(ii) If \(R \leq S,then \overline{S} \leq \overline{R}\)
This question involves understanding the properties of binary relations, specifically focusing on the concepts of subset inclusion (represented by '≤'), inverse relations (denoted by a superscript '-1'), and complement relations (denoted by an overline).
Statement (i) claims: If \( R \subseteq S \), then \( S^{-1} \subseteq R^{-1} \).
Let's break this down:
To check if this is true, let's consider the definition of subset inclusion for inverse relations. If \( R \subseteq S \), does it necessarily follow that \( S^{-1} \subseteq R^{-1} \)?
Consider an element \( (y, x) \in S^{-1} \). By the definition of the inverse relation, this implies that \( (x, y) \in S \).
Now, we know \( R \subseteq S \). If \( (x, y) \in S \), does it automatically mean \( (x, y) \in R \)? No, it does not. S could contain pairs that are not in R.
Let's test with an example: Let A = {a, b} and B = {a, b}. Let R = { (a, b) } Let S = { (a, b), (b, a) } Here, \( R \subseteq S \) is true. Now let's find the inverses: \( R^{-1} = \{ (b, a) \} \) \( S^{-1} = \{ (b, a), (a, b) \} \) Is \( S^{-1} \subseteq R^{-1} \)? This means is \( \{ (b, a), (a, b) \} \subseteq \{ (b, a) \} \)? No, this is false because \( (a, b) \) is in \( S^{-1} \) but not in \( R^{-1} \).
However, the reverse property, that if \( R \subseteq S \), then \( R^{-1} \subseteq S^{-1} \), is true. Let's prove this briefly: If \( (y, x) \in R^{-1} \), then \( (x, y) \in R \). Since \( R \subseteq S \), we have \( (x, y) \in S \). By the definition of inverse relation, this implies \( (y, x) \in S^{-1} \). Therefore, \( R^{-1} \subseteq S^{-1} \).
Since the statement requires \( S^{-1} \subseteq R^{-1} \), which is generally false, Statement (i) is false.
Statement (ii) claims: If \( R \subseteq S \), then \( \overline{S} \subseteq \overline{R} \).
Let's break this down:
To check if this is true, let's assume \( R \subseteq S \). We need to determine if \( \overline{S} \subseteq \overline{R} \).
Consider an element \( (x, y) \in \overline{S} \). By the definition of the complement relation, this means \( (x, y) \notin S \).
Since \( R \subseteq S \), if a pair \( (x, y) \) is not in S, it cannot be in R either. Therefore, \( (x, y) \notin R \).
If \( (x, y) \notin R \), then by the definition of the complement relation, \( (x, y) \in \overline{R} \).
So, we have shown that if \( (x, y) \in \overline{S} \), then \( (x, y) \in \overline{R} \). This implies that \( \overline{S} \subseteq \overline{R} \).
Therefore, Statement (ii) is true.
Based on the analysis:
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