1.
$A=\sin 6^{\circ}.\cos 48^{\circ}.\cos 24^{\circ}.\cos 12^{\circ}= \frac{1}{2\cos 6^{\circ}}.2.\sin 6^{\circ}.\cos 6\dot{^{\circ}}.\cos 48^{\circ}.\cos 24^{\circ}.\cos 12^{\circ}=\frac{1}{2\cos 6^{\circ}}.\sin 12^{\circ}.\cos 12^{\circ}.\cos 48^{\circ}.\cos 24^{\circ}=\frac{1}{4\cos 6^{\circ}}.\sin 24^{\circ}.\cos 24^{\circ}.\cos 48^{\circ}=\frac{1}{8\cos 6^{\circ}}.\sin 48^{\circ}.\cos 48^{\circ}=\frac{1}{16\cos 6^{\circ}}.\sin 96^{\circ}=\frac{1}{16}$
- quanghao98 yêu thích