Question : What will be the value of $\frac{\sin 30^{\circ} \sin 40^{\circ} \sin 50^{\circ} \sin 60^{\circ}}{\cos 30^{\circ} \cos 40^{\circ} \cos 50^{\circ} \cos 60^{\circ}}$?

Question : Evaluate the following.
$\sin 25^{\circ} \sin 65^{\circ}-\cos 25^{\circ} \cos 65^{\circ}$.

Question : Find the value of $\frac{\cos^2 15^{\circ}-\sin^2 15^{\circ}}{\cos^2 145^{\circ}+\sin^2 145^{\circ}}$.

Question : $\sin 600^\circ \cos 750^\circ+\sin 150^\circ \cos 240^\circ=?$

Question : $\frac{\cos 20^{\circ}}{\sin 70^{\circ}}+\frac{\cos \theta}{\sin \left(90^{\circ}-\theta\right)}=$_________,