[填空题]
The following diagra2yo.t,tulx;w m s rg/q78xazkcg 7x.sycb29n 0khows the parallelogram ABCD.
Let E denote the midpoint of [B D], $\mathbf{p}=\overrightarrow{\mathrm{BA}} $ and $ \mathbf{q}=\overrightarrow{\mathrm{BC}} $. Find each of the following vectors in terms of $\mathbf{p}$ and $\mathbf{q}$ .
1. $\overrightarrow{\mathrm{AC}}$ ;
2. $\overrightarrow{\mathrm{BE}}$ ;
3. $\overrightarrow{\mathrm{AE}}$ .