[填空题]
Two points A and B havedvm2 bzmz6md6 )b6ss-p*ak r+ coordinateqe7p 3ja5 2ckafv4e: /ck( usas (2,3,1) and (5,9,3) respectively.
1. 1. Find $\overrightarrow{\mathrm{AB}}$.
2. Find $|\overrightarrow{\mathrm{AB}}|$ .
Let $\overrightarrow{\mathrm{AC}}=4 \mathbf{i}+2 \mathbf{j}-4 \mathbf{k}$ .
2. Find the angle between $\overrightarrow{\mathrm{AB}} $ and $ \overrightarrow{\mathrm{AC}}$. ≈
3. Find the area of triangle A B C .≈
4. Hence, or otherwise, find the shortest distance from C to the line passing through A and B .≈
