Question

cos x - 2 sin ^2 +2=0

Answer 1

\(\Leftrightarrow cosx+2\left(1-sin^2x\right)=0\)

\(\Leftrightarrow cosx+2cos^2x=0\)

\(\Rightarrow\left[{}\begin{matrix}cosx=0\\cosx=-\dfrac{1}{2}\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=\dfrac{\pi}{2}+k\pi\\x=\pm\dfrac{2\pi}{3}+k2\pi\end{matrix}\right.\)