Determine whether each of the following relations are reflexive, symmetric and transitive:
Relation $R$ in the set $A$ of human beings in a town at a particular time given by
$R =\{(x, y): x $ is father of $y\}$
$R =\{( x , y ): x$ is the father of $y \}$
$( x , x ) \notin R$
As $x$ cannot be the father of himself.
$\therefore R$ is not reflexive.
Now, let $( x , y ) \notin R$
$\Rightarrow x$ is the father of $y$
$\Rightarrow y$ cannot be the father of $y$
Indeed, $y$ is the son or the daughter of $y$.
$\therefore(y, x) \notin R$
$\therefore R$ is not symmetric.
Now, let $(x, y) \in R$ and $(y, z) \notin R$
$\Rightarrow x$ is the father of $y$ and $y$ is the father of $z$.
$\Rightarrow x$ is not the father of $z$
Indeed, $x$ is the grandfather of $z$
$\therefore $ $( x , z ) \notin R$
$\therefore R$ is not transitive.
Hence, $R$ is neither reflexive, nor symmetric, nor transitive.
Show that the number of equivalence relation in the set $\{1,2,3\} $ containing $(1,2)$ and $(2,1)$ is two.
Let $R_1$ and $R_2$ be two relations on a set $A$ , then choose incorrect statement
Let $R_{1}$ and $R_{2}$ be relations on the set $\{1,2, \ldots, 50\}$ such that $R _{1}=\left\{\left( p , p ^{ n }\right)\right.$ : $p$ is a prime and $n \geq 0$ is an integer $\}$ and $R _{2}=\left\{\left( p , p ^{ n }\right)\right.$ : $p$ is a prime and $n =0$ or $1\}$. Then, the number of elements in $R _{1}- R _{2}$ is........
Let $P = \{ (x,\,y)|{x^2} + {y^2} = 1,\,x,\,y \in R\} $. Then $P$ is
Let $r$ be a relation from $R$ (set of real numbers) to $R$ defined by $r = \{(a,b) \, | a,b \in R$ and $a - b + \sqrt 3$ is an irrational number$\}$ The relation $r$ is