solve the trig equation sec(x)-2=0 for exact solutions in the interval
0<= x <= 2pi
That means,
$\displaystyle \sec x=2$
because secant is reciprocal function of cosine we have,
$\displaystyle \cos x=\frac{1}{2}$ for $\displaystyle 0<x<2\pi$
Thus,
$\displaystyle x=\frac{\pi}{6},\frac{11\pi}{6}$