[填空题]
Two points A and B have coordin e, eej )bmal4w:qhb:w5df5j,a. eriw io66 t,ck-cxe)tes (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 .≈
