Question

Câu 6, 7, 8 ạ

Answer 1

6. Có 4 vecto là \(\overrightarrow{BA};\overrightarrow{CA};\overrightarrow{DA};\overrightarrow{EA}\)

7. \(P=cos0+cos180^0+\left(cos20+cos160\right)+...+\left(cos80+cos100\right)\)

\(=\left(cos0-cos0\right)+\left(cos20-cos20\right)+...+\left(cos80-cos80\right)=0+0+...+0=0\)

8. \(\overrightarrow{BC}-\overrightarrow{AB}=\overrightarrow{BC}+\overrightarrow{BA}=\overrightarrow{BD}\)