[tex]\text{cos 30}^{\circ} = \frac{\text{cateto adjacente}}{\text{hipotenusa}} \ ou \ \text{sen 60}^{\circ} = \frac{\text{cateto oposto}}{\text{hipotenusa}} \\\\ \text{Em ambos os casos, temos:} \\\\ \frac{\sqrt{3}}{2} = \frac{x}{6} \\\\ \boxed{2x = 6 \sqrt{3} \ \text{cm}} \\\\
\circ \text{Pela lei dos cossenos:} \\\\
x^2 = 6^2 + 6^2 - 2 \cdot 6 \cdot 6 \cdot \text{cos 120}^\circ \\
x^2 = 72 - 72 \cdot (-\frac{1}{2}) \\
x^2 = 72 + 36 \\
x^2 = 108 \\
x = \sqrt{108} = \boxed{6 \sqrt{3} \ \text{cm}}
[/tex]
