## Trigonometry (11th Edition) Clone

Figure 37 shows that the graph of $y=\sec{x}$ is symmetric with respect to the y-axis. This means that the value of $y=\sec{x}$ when $x=-\pi$ is the same as its value when $x=\pi$, and this is true for all non-zero values of $x$. Therefore, $\sec{x} = \sec{(-x)}$.