[tex]\displaystyle\bf\\Sin\alpha =0,(3)=\frac{3}{9}=\frac{1}{3} \\\\\\36Cos\Big(\alpha +\frac{\pi }{3} \Big)Cos\Big(\frac{\pi }{3} -\alpha \Big)=\\\\\\=36\cdot \frac{1}{2} \cdot\Big[ Cos\Big(\alpha +\frac{\pi }{3} -\frac{\pi }{3}+\alpha \Big)+Cos\Big(\alpha +\frac{\pi }{3} +\frac{\pi }{3}-\alpha \Big)\Big]= \\\\\\=18\cdot\Big(Cos2\alpha +Cos\frac{2\pi }{3}\Big)=18\cdot\Big(Cos2\alpha -\frac{1}{2}\Big) =18Cos2\alpha -9=\\\\\\=18\cdot(1-2Sin^{2}\alpha )-9=18-36Sin^{2} \alpha -9=[/tex]

[tex]\displaystyle\bf\\=9-36\cdot\Big(\frac{1}{3}\Big)^{2} =9-36\cdot\frac{1}{9} =9-4=5[/tex]