Physics - Vectors Question with Solution | TestHub

Hints: Here $\vec{a}+\vec{b}=\vec{c}\&c=a+b$ Now, $c=\sqrt{a^2+b^2+2ab\cos \theta }$ $\begin{array}{rl}& (a+b)=\sqrt{a^2+b^2+2ab\cos \theta }\\ & a^2+b^2+2ab=a^2+b^2+2ab\cos \theta \\ & \cos \theta =1,\theta =0^{\circ }\end{array}$