Question

cho 2 hình bình hành ABCD và AB'C'D' có chung đỉnh A . CMR

\(\overrightarrow{B'B}+\overrightarrow{CC'}+\overrightarrow{D'D}=\overrightarrow{0}\)

Answer 1

\(\overrightarrow{CC'}=\overrightarrow{CB}+\overrightarrow{BB'}+\overrightarrow{B'C'}=\overrightarrow{BB'}+\overrightarrow{DA}+\overrightarrow{AD'}=\overrightarrow{BB'}+\overrightarrow{DD'}\)

\(\Rightarrow\overrightarrow{CC}'=-\overrightarrow{B'B}-\overrightarrow{D'D}\)

\(\Rightarrow\overrightarrow{B'B}+\overrightarrow{CC'}+\overrightarrow{D'D}=\overrightarrow{B'B}-\overrightarrow{B'B}-\overrightarrow{D'D}+\overrightarrow{D'D}=\overrightarrow{0}\)