Cho hình chữ nhật ABCD tâm O
AB = 3 , AD = 4
a / Chứng minh:
\(\overrightarrow{DO}+\overrightarrow{AO}=\overrightarrow{DC}\)
\(\overrightarrow{OB}+\overrightarrow{OC}=\overrightarrow{AB}\)
\(\overrightarrow{BA}+\overrightarrow{DB}=\overrightarrow{CB}\)
b/ Tính
\(\left|\overrightarrow{AB}+\overrightarrow{CB}\right|\)
\(\left|\overrightarrow{OD}+\overrightarrow{OC}\right|\)
\(\left|\overrightarrow{DA}+\overrightarrow{OC}\right|\)
\(\left|\overrightarrow{BO}+\overrightarrow{OC}+\overrightarrow{BA}\right|\)
