$$\tan A+2 \tan 2 A+4 \tan 4 A+8 \cot 8 A=$$

$$\begin{aligned} & \cos \left(36^{\circ}-A\right) \cos \left(36^{\circ}+A\right)+\cos \left(54^{\circ}+A\right) \cos \\ & \left(54^{\circ}-A\right)= \end{aligned}$$

The pdf of a continuous r.v. $$X$$ is given by $$f(x)=\frac{x}{8}, 0 < x < 4=0$$, otherwise, then $$P(X \leq 2)$$ is

If $$f(x)=\frac{|x|}{x}$$, for $$x \neq 0$$ $$=1$$, for $$x=0$$, then tre function is