A complex number $\alpha \in \mathbb{C}$ is called algebraic if there is a non-zero polynomial $P(x) \in \mathbb{Q}\left[x\right]$ with rational coefficients such that $P(\alpha)=0$. Which of the following statements is true?
- There are only finitely many algebraic numbers
- All complex numbers are algebraic
- $\sin (\frac{\pi}{3})+ \cos (\frac{\pi}{4}$) is algebraic
- None of the above