преобразовать в произведение cos(a+п/6)-cos*п/6​

[tex]cos(a+\frac{\pi }{6} ) - cos(\frac{\pi }{6} )\\cos(a)cos(\frac{\pi }{6} ) - sin(a)sin(\frac{\pi }{6} ) - \frac{\sqrt{3} }{2} \\cos(a)*\frac{\sqrt{3} }{2} - \frac{sin(a)}{2} * \frac{1}{2} - \frac{\sqrt{3} }{2} \\\frac{\sqrt{3}cos(a) }{2} - \frac{sin(a)}{2} - \frac{\sqrt{3} }{2} \\\frac{\sqrt{3}cos(a)-sin(a)-\sqrt{3} }{2} .[/tex]