Для начала упростим выражение.
$$sin(855°) = sin(855° - 2 \cdot 360°) = sin(855° - 720°) = sin(135°)$$
$$sin(135°) = sin(180° - 45°) = sin(45°) = \frac{\sqrt{2}}{2}$$
$$12\sqrt{32} = 12\sqrt{16 \cdot 2} = 12 \cdot 4\sqrt{2} = 48\sqrt{2}$$
$$48\sqrt{2} \cdot \frac{\sqrt{2}}{2} = \frac{48 \cdot 2}{2} = 48$$
Ответ: 48