#### Answer

Since for any $ x\in R $, then $ x^2\in R $, and by Theorem 3 $ f(x)= \cos x^2$ is a continuous function.

#### Work Step by Step

We are given the function $ f(x)= \cos x^2$. Since for any $ x\in R $, then $ x^2\in R $, and by Theorem 3 $ f(x)= \cos x^2$ is a continuous function.