Find the angle 𝜃 θ between the vectors 𝐚=10𝐢−𝐣−5𝐤 a = 10 i − j − 5 k and 𝐛=2𝐢+𝐣−8𝐤 b = 2 i + j − 8 k

Question

Find the angle  between the vectors  and 

Answer 1

θ = cos^-1(a•b)/(|a||b|)

a•b = 20-1+40=59

|a| = √(100+1+25) = √126

|b| = √(4+1+64) = √69

|a||b| = √(126•69) = 93.24

θ = cos^-1(59/93.24) = 50.75° = 0.89 radians

The problem ended with "and". What else is needed to be evaluated?