How these 3 vectors form a right triangle? $ A = 2\hat{i} -2\hat{j} + 3\hat{k}$
$ B = 2\hat{i} -\hat{j} + 3\hat{k}$
$ C = \hat{i} -\hat{j} - \hat{k}$
My textbook demands that these 3 vectors form right triangle. Firstly, I think these 3 vectors don't form a triangle. 
Actual Condition for triangle : $ A\pm{B}\pm{C} = 0$ and this is flase for these 3 vectors.
Am I wrong?

The given vectors are position vectors. To get the vectors representing the sides of the triangle do $A-B, B-C, C-A$. You will find that $\angle B = 90^{\circ}$
