Giải các pt lượng giác sau
1) \(cos^2\left(x-\frac{\pi}{6}\right)-sin^2\left(x-\frac{\pi}{6}\right)=sin\left(x+\frac{\pi}{3}\right)\)
2) \(sin^4-sin^4\left(x+\frac{\pi}{2}\right)=sin\left(x+\frac{\pi}{3}\right)\)
3) \(8cos^3\left(x-\frac{\pi}{3}\right)-1=0\)