1. The number of solutions to the equation $\sin |x|=|\cos x|$ in the interval $[-10 \pi, 10 \pi]$ is $\qquad$
1. E0.

Since $\sin |x|$ and $|\cos x|$ are both even functions, we only need to consider the number of solutions within $[0,10 \pi]$. In this case, the equation becomes $\sin x=|\cos x|$. When $0 \leqslant x \leqslant \frac{\pi}{2}$, the equation becomes $\sin x=\cos x$, which has only one solution $x=\frac{\pi}{4}$; when $\frac{\pi}{2} \leqslant x \leqslant \pi$, the equation becomes $\sin x=-\cos x$, which has only one solution $x=\frac{3 \pi}{4}$. Therefore, $\sin x=|\cos x|$ has 2 roots in $[0,2 \pi]$, and thus $\sin |x|=|\cos x|$ has $10 \times 2=20$ solutions in $(-10 \pi, 10 \pi)$.