The proof that a 60 degree angle cannot be trisected leads to which kind of equation?

1. The triple-angle formula relates cos 60 degrees and cos 20 degrees. 2. It gives 8x^3 - 6x - 1 = 0, a cubic. 3. Its root has degree 3, which is not a power of two, so it is not constructible. _Source: Wikipedia, Angle trisection, section Proof of impossibility_