Question

If A is the point (1,−1,2),B is the point (−1,2,2) and C is the point (4,3,0), find the direction cosines of BA and BC, and hence show that the angle ABC=69∘14′.

Answer 1

BA: L_BA = (2/√13, -3/√13, 0)

BC: L_BC = (5/√30, 1/√30, -2/√30)