minimal polynomial, $E_p=\cos\frac{2\pi}{p} + i\sin\frac{2\pi}{p}$

Question

How to get a minimal polynomial for an algebraic number: $E_p=\cos\frac{2\pi}{p} + i\sin\frac{2\pi}{p}$?

$x=\cos\frac{2\pi}{p} + i\sin\frac{2\pi}{p}$ /$^{p}$

$x^{p}=\cos2\pi + i\sin2\pi$

$x^{p}=1$

$x^{p}-1=0$

$(x-1)(x^{p-1} + x^{p-2} + x^{p-3} +\cdots+ 1)=0$

$(x-1)\dfrac{1-x^p}{1-x}=0$

I don't know what to do now. I have to get irreducible polynomial.