По теореме косинусов: $$AC^2 = AB^2 + BC^2 - 2 \cdot AB \cdot BC \cdot \cos B$$ $$AC^2 = 8^2 + (4\sqrt{6})^2 - 2 \cdot 8 \cdot 4\sqrt{6} \cdot \cos 60°$$ $$AC^2 = 64 + 16 \cdot 6 - 64\sqrt{6} \cdot \frac{1}{2}$$ $$AC^2 = 64 + 96 - 32\sqrt{6}$$ $$AC^2 = 160 - 32\sqrt{6}$$ $$AC = \sqrt{160 - 32\sqrt{6}}$$ По теореме синусов: $$\frac{AC}{sin B} = \frac{BC}{sin A}$$ $$\frac{\sqrt{160 - 32\sqrt{6}}}{sin 60°} = \frac{4\sqrt{6}}{sin A}$$ $$sin A = \frac{4\sqrt{6} \cdot sin 60°}{\sqrt{160 - 32\sqrt{6}}}$$ $$sin A = \frac{4\sqrt{6} \cdot \frac{\sqrt{3}}{2}}{\sqrt{160 - 32\sqrt{6}}}$$ $$sin A = \frac{2\sqrt{18}}{\sqrt{160 - 32\sqrt{6}}}$$ $$sin A = \frac{6\sqrt{2}}{\sqrt{160 - 32\sqrt{6}}}$$ $$A = arcsin(\frac{6\sqrt{2}}{\sqrt{160 - 32\sqrt{6}}})$$
Ответ: $$arcsin(\frac{6\sqrt{2}}{\sqrt{160 - 32\sqrt{6}}})$$