If $A+B=\frac{\pi}{4}$, then $\frac{\cos B-\sin B}{\cos B+\sin B}=$

If $7 \cos \theta-\sin \theta=5$ and $\tan \theta>0$, then $\tan \theta=$

$$ \sin ^3 10^{\circ}+\sin ^3 50^{\circ}-\sin ^3 70^{\circ}= $$

$$ \begin{aligned} \frac{1}{\sin 1^{\circ} \sin 2^{\circ}}+\frac{1}{\sin 2^{\circ} \sin 3^{\circ}}+\frac{1}{\sin 3^{\circ} \sin 4^{\circ}} & +\frac{1}{\sin 89^{\circ} \sin 90^{\circ}}= \end{aligned} $$