question_answer

What should be the angle \[\theta \] between two vectors \[\vec{A}\] and \[\vec{B}\] for their resultant \[\vec{R}\] to be minimum?

Answer:

                \[R=\sqrt{{{A}^{2}}+{{B}^{2}}+2AB\cos \theta }\] R will be minimum when \[\cos \theta =-1\] or \[\theta =\mathbf{18}{{\mathbf{0}}^{\mathbf{o}}}\] \[{{R}_{\min }}=A\tilde{\ }B.\]