Tolong jawab nomor 3

Bab Trigonometri

∠ABC
= 180° - 120°
= 60°

Luas = (AB × BC × sin ∠ABC)/2
27 × 2 = 12 × BC × sin 60°
54/12 = BC × 1/2 √3
9/2 × 2 = BC × √3
9/√3 = BC
BC = 9/√3 × √3/√3
BC = 9√3/3
BC = 3√3 cm