The value of $$\tan \left(\frac{\pi}{8}\right)$$ is _________.

The value of $$\tan \frac{\pi}{8}$$ is

If $$\cos 2 B=\frac{\cos (A+C)}{\cos (A-C)}$$. Then $$\tan A, \tan B, \tan C$$ are in

If $$\sin 18^{\circ}=\frac{\sqrt{5}-1}{4}$$, then $$\cos ^2 48^{\circ}-\sin ^2 12^{\circ}$$ has the value