$\frac{\cos 9^\circ + \sin 9^\circ}{\cos 9^\circ - \sin 9^\circ} = $

If $A=35^{\circ}, B=15^{\circ}$ and $C=40^{\circ}$,then $\tan A \cdot \tan B+\tan B \cdot \tan C+\tan C \cdot \tan A$ is equal to

The value of $\cos 15^{\circ} - \sin 15^{\circ}$ is ......

Two ships leave a port from a point at the same time. One goes with a velocity of $3 \text{ km/h}$ along North-East making an angle of $45^{\circ}$ with the East direction and the other travels with a velocity of $4 \text{ km/h}$ along South-East making an angle of $15^{\circ}$ with the East direction. Then, the distance between the ships at the end of two hours is

$\frac{\sin 3\theta + \sin 5\theta + \sin 7\theta + \sin 9\theta}{\cos 3\theta + \cos 5\theta + \cos 7\theta + \cos 9\theta} = $

The value of $\frac{\tan 70^o - \tan 20^o}{\tan 50^o} = $