\(\Omega< a< \dfrac{3}{2}\Omega\)
=>\(sina< 0\)
\(sin^2a+cos^2a=1\)
=>\(sin^2a=1-\dfrac{1}{16}=\dfrac{15}{16}\)
=>\(sina=-\dfrac{\sqrt{15}}{4}\)
\(sin\left(a-\dfrac{2}{3}\Omega\right)=sina\cdot cos\left(\dfrac{2}{3}\Omega\right)-cosa\cdot sin\left(\dfrac{2}{3}\Omega\right)\)
\(=-\dfrac{\sqrt{15}}{4}\cdot\dfrac{-1}{2}-\dfrac{-1}{4}\cdot\dfrac{\sqrt{3}}{2}\)
\(=\dfrac{\sqrt{15}+\sqrt{3}}{8}\)




