Urč presnú hodnotu:
\( \cos 195^{\circ} \)
\( -\frac{\sqrt{2}+\sqrt{3}}{4} \)
\( -\frac{\sqrt{6}+\sqrt{2}}{4} \)
\( \frac{\sqrt{6}-\sqrt{2}}{4} \)
\( \frac{\sqrt{3}-\sqrt{6}}{4} \)