Chapter 1, Equations and Graphs - Section 1.7 - Solving Inequalities - 1.7 Exercises - Page 148: 9

$-5, -1, \sqrt5, 3, 5$

Since the fractions both have a numerator of $1$, then the fraction $\frac{1}{x}$ will be less than or equal to $\frac{1}{2}$ when $x \ge 2$ or when $x$ is negative. Thus, the elements of $S$ that satisfy the inequality are: $-5, -1, \sqrt5, 3, 5$