Answer
$\{0,\pm2\pi\}$
Work Step by Step
Step 1. Rewrite the equation as $sec(x)-1=0$ and define a function $f(x)=sec(x)-1$.
Step 2. Graph the function in the interval of $[-2\pi,2\pi]$ as shown in the figure.
Step 3. Identify zeros as $x=0,\pm2\pi$
Step 4. We conclude the solution set in $[-2\pi,2\pi]$ is $\{0,\pm2\pi\}$
