a: \(sinx\cdot sin\left(x-\dfrac{\Omega}{18}\right)=0\)
=>\(\left[{}\begin{matrix}sinx=0\\sin\left(x-\dfrac{\Omega}{18}\right)=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=k\Omega\\x-\dfrac{\Omega}{18}=k\Omega\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=k\Omega\\x=k\Omega+\dfrac{\Omega}{18}\end{matrix}\right.\)
b: \(sin\left(\Omega-x\right)-cosx=0\)
=>\(sin\left(\Omega-x\right)=cosx=sin\left(\dfrac{\Omega}{2}-x\right)\)
=>\(\left[{}\begin{matrix}\Omega-x=\dfrac{\Omega}{2}-x+k2\Omega\\\Omega-x=\Omega-\left(\dfrac{\Omega}{2}-x\right)+k2\Omega\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}\Omega=\dfrac{\Omega}{2}+k2\Omega\\\Omega-x=\dfrac{\Omega}{2}+x+k2\Omega\end{matrix}\right.\Leftrightarrow\Omega-x=\dfrac{\Omega}{2}+x+k2\Omega\)
=>\(-2x=-\dfrac{\Omega}{2}+k2\Omega\)
=>\(x=\dfrac{\Omega}{4}-k\Omega\)
