$\tan 3A - \tan 2A - \tan A = $

The value of $\cot 7\frac{1}{2}^{\circ} + \tan 67\frac{1}{2}^{\circ} - \cot 67\frac{1}{2}^{\circ} - \tan 7\frac{1}{2}^{\circ}$ is:

If $\sin \alpha = \frac{336}{625}$ and $450^\circ < \alpha < 540^\circ$,then $\sin \left( \frac{\alpha}{4} \right) = $

If $\sinh x = \frac{5}{12}$,then $\cosh \frac{x}{2} =$

If $\tan A = \frac{1 - \cos B}{\sin B},$ find $\tan 2A$ in terms of $\tan B$.

If $\frac{\sec 8\theta - 1}{\sec 4\theta - 1} = \frac{a + b \tan^2 2\theta}{1 + c \tan^2 2\theta + d \tan^4 2\theta}$ (where $\theta \neq \frac{n\pi}{16}, n \in I$),then the value of $(a - b + c - d)$ is -