To solve the problem, we are given the value of $\sec \theta$ and are asked to find the value of $\cos \theta$.
1. Understanding the Identity:
By definition, the secant function is the reciprocal of the cosine function:
$ \sec \theta = \frac{1}{\cos \theta} $
2. Substituting the Given Value:
We are given:
$ \sec \theta = \frac{2}{\sqrt{3}} $
So,
$ \cos \theta = \frac{1}{\sec \theta} = \frac{1}{\frac{2}{\sqrt{3}}} = \frac{\sqrt{3}}{2} $
Final Answer:
$ \cos \theta = \frac{\sqrt{3}}{2}