По теореме синусов:
$$\frac{AC}{sin B} = \frac{AB}{sin C}$$
$$\frac{4\sqrt{2}}{sin 45°} = \frac{6}{sin C}$$
$$sin C = \frac{6 \cdot sin 45°}{4\sqrt{2}} = \frac{6 \cdot \frac{\sqrt{2}}{2}}{4\sqrt{2}} = \frac{3\sqrt{2}}{4\sqrt{2}} = \frac{3}{4}$$
Ответ: $$\frac{3}{4}$$