Question

In a triangle OAC, if B is the mid-point of side AC and $\underset{OA}{\to }=\underset{a}{\to },\underset{OB}{\to }=\underset{b}{\to }$, then what is $\underset{OC}{\to }$ ?

Answer 1

As B is the mid-point of side AC so, $\underset{OB}{\to }=\frac{\underset{OA}{\to }+\underset{OC}{\to }}{2}$ i.e., $\overrightarrow{b}=\frac{\underset{a}{\to }+\underset{OC}{\to }}{2}$. Therefore, $\underset{OC}{\to }=2\overrightarrow{b}-\overrightarrow{a}$.