7. Let $x \in\left(\frac{\pi}{2}, \frac{2 \pi}{3}\right]$, and let $A=\sin (\sin x), B=\cos (\cos x), C=\sin (\cos x), D=\cos (\sin x)$. Arrange $A, B, C, D$ in ascending order: $\qquad$ .
7. $C<D<A<B$. Since $x \in\left(\frac{\pi}{2}, \frac{2 \pi}{3}\right]$, we know $\sin (\sin x)=\cos \left[\frac{\pi}{2}-\sin x\right]$. And $\frac{\sqrt{3}}{2} \leqslant \sin x<1$, we get $\cos \frac{1}{2}(\pi-$ $\sqrt{3}) \leqslant \sin (\sin x)<\cos \frac{1}{2}(\pi-2)$.