Respuesta :

[tex]
\cos^2(x)+2\cos(x)+1=0\\\\
(\cos(x)+1)^2=0\\\\
\text{So:}\\\\
\cos(x)+1=0\\\\
\cos(x)=-1\\\\
\boxed{x=\pi+2k\pi},~k\in\mathbb{Z}[/tex]
Hope this helps you.
Ver imagen Аноним