question_answer

The vectors \[\vec{a},\text{ }\vec{b}\]and \[\vec{c}\] are equal in length and taken pain wise, they make equal angles. \[\vec{a}=\hat{i}+\hat{j},\vec{b}=\hat{j}+\hat{k}\]and\[\vec{c}\]makes an obtuse angle with x-axis, then \[\vec{c}\] =

A)  \[\hat{i}+\hat{k}\]       

B)  \[-\,\hat{i}+4\hat{j}-\hat{k}\]

C)  \[\frac{1}{3}(-\,\hat{i}+4\hat{j}-\hat{k})\]

D)         \[\frac{1}{3}(\,\hat{i}-4\hat{j}+\hat{k})\]