The number of ways that 8 beads of different colours can be strung to form a necklace is

In $\Delta ABC$, if $\angle A = 90^\circ$, then $\sin(B - C) = $

The value of $\cos^2 10^\circ - \cos 10^\circ \cos 50^\circ + \cos^2 50^\circ$ is equal to....

The general solution of $\cos 4\theta = \cos 3\theta$ is $\theta = $.....