Nihh tolong jawab soalnya ??

[tex] \cos60 = \frac{AB}{AC} \\\cos60 = \frac{AB}{18} \\ \frac{1}{2} = \frac{AB}{18} \\ 2AB = 18 \\AB = 9[/tex]

Jadi, jawabannya C (9 cm).

AB = cos A × AC
AB = cos 60° × 18 cm
AB = 0,5 × 18 cm
AB = 9 cm