16. As shown in the figure, in the right triangular prism $A B C - A _ { 1 } B _ { 1 } C _ { 1 }$, given $A C \perp B C$. Let D be the midpoint of $A B _ { 1 }$,\\
$B _ { 1 } C \cap B C _ { 1 } = E$ .\\
Prove: (1) $D E \parallel$ plane $A A _ { 1 } C C _ { 1 }$\\
(2) $B C _ { 1 } \perp A B _ { 1 }$\\
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