CORRECTION: at the end I forgot to divide by 2 both sides.Ans: cos ^ 2 (pi/8) = (sq rt 2 + 2 )/4Thanks to Herbert for pointing that out. ... <看更多>

please like and subscribe my YouTube channel # cos ( 2π -x)=cosx and # cos ( 2π +x)=cosx solve#trigonometricidentiescos(2π-x)=cosx and ... ... <看更多>

This is a proof using Galois theory posted on Wilson Ong's Blog. We know cos(2π)=1 and cos(π)=−1. Let n≥3 be a positive integer and ... ... <看更多>