3. In $\triangle A B C$, it is known that $\sin A=10 \sin B \sin C, \cos A=10 \cos B \cos C$, then the value of $\tan A$ is . $\qquad$
$$
\cos A - \sin A = 10 \cos (B+C) = -10 \cos A \Rightarrow \sin A = 11 \cos A \Rightarrow \tan A = 11
$$