I stumble upon this problem which says:
The set $\{ x\in\mathbb R: x\sin x\le 1, x\cos x \le 1\}$ is contained in $\mathbb R$.Then which of the following about the set is true:
- a bounded closed set
- a bounded open set
- an unbounded closed set
- an unbounded open set.
Any kind of hints will be helpful.