Recall that for any binary relation R on set A. We have,

R is reflexive if for all x ∈ A, xRx.

R is symmetric if for all x, y ∈ A, if xRy, then yRx.

R is transitive if for all x, y, z ∈ A, if xRy and yRz, then xRz.

Using these properties, we can define R on A.

A = {1, 2, 3, 4}

We need to define a relation (say, R) which is reflexive, symmetric and transitive.

The relation must be defined on A.

Reflexive Relation:

R = {(1, 1), (2, 2), (3, 3), (4, 4)}

Or simply shorten it and write,

R = {(1, 1), (2, 2)} …(1)

Symmetric Relation:

R = {(1, 2), (2, 1), (2, 3), (3, 2), (3, 4), (4, 3)}

Or simply shorten it and write,

R = {(1, 2), (2, 1)} …(2)

Combine results (1) and (2), we get

R = {(1, 1), (2, 2), (1, 2), (2, 1)}

It is reflexive, symmetric as well as transitive as per definition.

Similarly, we can find other combinations too.

Thus, we have got the relation which is reflexive, symmetric as well as transitive.