Question

\(4cosxcos2x=cosx-\sqrt{3}sinx\)

Giải hộ em với ạ ! :)))

 

Answer 1

\(\Leftrightarrow2cosx+2cos3x=cosx-\sqrt{3}sinx\)

\(\Leftrightarrow\dfrac{1}{2}cosx+\dfrac{\sqrt{3}}{2}sinx=-cos3x\)

\(\Leftrightarrow cos\left(x-\dfrac{\pi}{3}\right)=cos\left(\pi-3x\right)\)

\(\Leftrightarrow...\)