化简下列各式:

(1) $\frac{\tan (2 \pi-\alpha) \cdot \sin (-2 \pi-\alpha) \cdot \cos (6 \pi-\alpha)}{\cos (\alpha-\pi) \cdot \sin (5 \pi-\alpha)}$;

(2) $\frac{\sqrt{1+2 \sin 290^{\circ} \cos 430^{\circ}}}{\sin 250^{\circ}+\cos 790^{\circ}}$.
(1) 原式 $=\frac{\frac{\sin (2 \pi-\alpha)}{\cos (2 \pi-\alpha)} \cdot \sin (-\alpha) \cdot \cos (-\alpha)}{\cos (\pi-\alpha) \cdot \sin (\pi-\alpha)}=-\frac{\sin \alpha}{\cos \alpha} \cdot \frac{-\sin \alpha}{-\cos \alpha} \cdot \frac{\cos \alpha}{\sin \alpha}$

$=-\tan \alpha$.

(2) 原式 $=\frac{\sqrt{1+2 \sin \left(360^{\circ}-70^{\circ}\right) \cos \left(360^{\circ}+70^{\circ}\right)}}{\sin \left(180^{\circ}+70^{\circ}\right)+\cos \left(720^{\circ}+70^{\circ}\right)}=\frac{\sqrt{1-2 \sin 70^{\circ} \cos 70^{\circ}}}{-\sin 70^{\circ}+\cos 70^{\circ}}$

$=\frac{\left|\cos 70^{\circ}-\sin 70^{\circ}\right|}{\cos 70^{\circ}-\sin 70^{\circ}}=\frac{\sin 70^{\circ}-\cos 70^{\circ}}{\cos 70^{\circ}-\sin 70^{\circ}}=-1$