Given f(x)=∑n=1∞sin(nx)2nf(x) = \sum_{n=1}^{\infty} \frac{\sin(nx)}{2^n}f(x)=∑n=1∞2nsin(nx), which statement is true?
fff is continuous but not differentiable
fff is differentiable on R\mathbb{R}R
fff is not continuous at x=0x=0x=0
fff is a polynomial