Mathematics - Vector Question with Solution | TestHub

Since $\vec{a}=8\vec{b}$ $$\overrightarrow{\mathrm{c}}=-7\overrightarrow{\mathrm{b}}$$ $\therefore \vec{a}$ and $\vec{b}$ are like vectors and $\vec{b}$ and $\vec{c}$ are unlike. $\Rightarrow \vec{a}$ and $\vec{c}$ will be unlike Hence, angle between $\vec{a}$ and $\vec{c}=\pi$.