Open 213cy opened 7 years ago
c^2=|\overrightarrow{C}|^2=|\overrightarrow{A}-\overrightarrow{B}|^2=(\overrightarrow{A}-\overrightarrow{B})\cdot (\overrightarrow{A}-\overrightarrow{B}) =a^2+b^2-2ab\cos(\theta )