Question 63
Prove that there is no integer $n \ge 2$ such that
$$
f(x) = \cos(x\sqrt{1}) + \cos(x\sqrt{2}) + \dots + \cos(x\sqrt{n})
$$
is a periodic function.
$$
f(x) = \cos(x\sqrt{1}) + \cos(x\sqrt{2}) + \dots + \cos(x\sqrt{n})
$$
is a periodic function.