Question 1 of 10 What is the domain of $y=\cos x$ ? A. $x \neq n \pi$ B. $-1 \leq y \leq 1$ C. $x \neq \frac{\pi}{2}+n \pi$ D. All real numbers

Step 1 ：Given the function: \(y = \cos{x}\)

Step 2 ：The domain of a function is the set of all possible input values (x-values) for which the function is defined.

Step 3 ：For the cosine function, it is defined for all real numbers.

Step 4 ：\(\boxed{\text{The domain of } y = \cos(x) \text{ is all real numbers (D)}}\)