Question

What is the domain of `f(x)=cosx`?

Answer 1

Domain of `f(x)` is `RR`. See below

Explanation:

`f(x)=cosx` is a circular function defined in the goniometric circle by `x` coordinate. Thus is defined for all positions in that circle. But `f(x)` repeat his values each lap. For this reason, we say `cosx` is a periodic function. See the graph graph{cosx [-12.66, 12.65, -6.33, 6.33]}

The range of `cosx` is (as we can see in graph) `[-1,1]`