\(\cos\left(x+\frac{\pi}{3}\right)+\cos x=\frac{3}{2}-4\sin\left(\frac{x}{2}\right)\cdot\sin\left(\frac{x}{2}+\frac{\pi}{6}\right)\)

\(\sin\left(3x+\frac{\pi}{4}\right)+8\sin^2x-\sqrt{2}\sin x=2\)

giair pt:\(\frac{1-\cos x\cos2x}{\sin2x}-\frac{1}{\cos x}=4\sin^2x-\sin x-1\)

giải phương trình: \(\frac{\cos x}{\cos3x}-\frac{\cos5x}{\cos x}+8\sin^2\left(2x+\frac{11\pi}{2}\right)=4\left(1+\cos2x\right)\)