# Let P = {p, q, n, m} where p, q, n, m are the lines forming the sides of a rectangle.  Write the relation of “is perpendicular to” in the roster form.

If ‘a’ is “perpendicular to” ‘b’ is denoted by a $\perp$ b, then we have p $\perp$ q, q $\perp$ p, m $\perp$ p, p $\perp$ m, m $\perp$ n, n $\perp$ m, n $\perp$ q, q $\perp$ n.
$\therefore$ In the roster form, the relation ‘is perpendicular’ is given by
‘$\perp$’ = {(p, q), (q, p), (m, p), (p, m), (m, n), (n, m), (n, q), (q, n)}