3. Given $t \neq 0, \cos (x+b)=\frac{p^{5}+i}{2 p^{2}}$, $\cos (\alpha-\beta)=\frac{p-1}{2 p^{2}}$. Then express $\operatorname{tg} \alpha \cdot \operatorname{tg} \beta$ in terms of $p$ $=$ $\qquad$
3. $-\frac{1}{p}$