已知平行四边形和其对角线如图，设 \(\overrightarrow{A C}=\vec{a}, \overrightarrow{B D}=\vec{b}\) ，请按顺序求 \(\overrightarrow{A B}, \overrightarrow{B C}, \overrightarrow{C D}, \overrightarrow{D A}\)
已知平行四边形和其对角线如图，设 \(\overrightarrow{A C}=\vec{a}, \overrightarrow{B D}=\vec{b}\) ，请按顺序求 \(\overrightarrow{A B}, \overrightarrow{B C}, \overrightarrow{C D}, \overrightarrow{D A}\)