2. Найдем угол B:
$$∠B = 180° - ∠A - ∠C$$ $$∠B = 180° - 120° - 45° = 15°$$
Применим теорему синусов:
$$\frac{BC}{sin(A)} = \frac{AB}{sin(C)}$$ $$BC = \frac{AB \cdot sin(A)}{sin(C)}$$ $$BC = \frac{3\sqrt{2} \cdot sin(120°)}{sin(45°)}$$ $$BC = \frac{3\sqrt{2} \cdot \frac{\sqrt{3}}{2}}{\frac{\sqrt{2}}{2}}$$ $$BC = 3\sqrt{3}$$
Ответ: $$3\sqrt{3}$$ см.