\(\Leftrightarrow sinx.cosx+2sinx+\left(1-cos^2x-3cosx-3\right)=0\)
\(\Leftrightarrow sinx\left(cosx+2\right)-\left(cosx+1\right)\left(cosx+2\right)=0\)
\(\Leftrightarrow\left(sinx-cosx-1\right)\left(cosx+2\right)=0\)
\(\Leftrightarrow sinx-cosx=1\)
\(\Leftrightarrow sin\left(x-\frac{\pi}{4}\right)=\frac{\sqrt{2}}{2}\)
\(\Leftrightarrow...\)