\begin{equation*}
\begin{split}
AB^2 & = AC^2 + BC^2 - 2 \:.\: AC \:.\: BC \:.\: \cos C \\\\
AB^2 & = 4^2 + 6^2 - 2 \:.\: 4 \:.\: 6 \:.\: \cos 60^{\text{o}} \\\\
AB^2 & = 16 + 36 - 2 \:.\: 4 \:.\: 6 \:.\: \tfrac{1}{2} \\\\
AB^2 & = 28 \\\\
AB & = \pm 2 \sqrt{7} \text{ cm}
\end{split}
\end{equation*}
Karena panjang sisi harus bernilai positif, gunakan\(AB = 2 \sqrt{7} \text{ cm}\)
