1. Let $A=\sin \left(\sin \frac{3}{8} \pi\right), B=\sin \left(\cos \frac{3}{8} \pi\right), C=\cos \left(\sin \frac{3}{8} \pi\right), D=$ $\cos \left(\cos \frac{3}{8} \pi\right)$, compare the sizes of $A$, $B$, $C$, and $D$.