The vectors a =2 i - j + k, b = i -3 j -5 k and c =-3 i +4 j +4 k represents the sides of

The vectors $\displaystyle \vec{a}=2 \hat{i}-\hat{j}+\hat{k}, \vec{b}=\hat{i}-3 \hat{j}-5 \hat{k}$ and $\displaystyle \vec{c}=-3 \hat{i}+4 \hat{j}+4 \hat{k}$ represents the sides of