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

If $$\cot (A+B)=0$$, then $$\sin (A+2 B)$$ is equal to

If $$2 \cos \theta=x+\frac{1}{x}$$, then $$2 \cos 3 \theta=$$

If $$\frac{\cos (A+B)}{\cos (A-B)}=\frac{\sin (C+D)}{\sin (C-D)}$$, then $$\tan A \tan B \tan C=$$