Question

The angle between two vector I+j and j+k is

Answer 1

Hi friend here is your answer.

#####################

cosx=[(i+j).(j+k)]/2=1/2

cosx=cos60°

x=60° ans.

#####################

Answer 2

Angle θ between the vectors (i+j) & (j+k) such that 0≤θ≤π is given by dot product as follows

(i+j)⋅(j+k)=i⋅j+j⋅j+i⋅k+j⋅k

|i+j||j+k|cosθ=1

2–√2–√cosθ=1

2cosθ=1

cosθ=12

cosθ=cos60∘

θ=60∘