what is the angle between (i+j) and (k+j)?

let vector a = i^ + j^

and vector b = k^ + j^

 

Let the angle between a and b is ?, then

 

a.b = a b cos?

 

(i^ + j^).(k^ + j^) = sqrt(1+1)sqrt(1+1) cos?

 

0 + 0 + 0 + 1 = 2 cos ?

 

cos? = 1/2

 

? = 60⁰