Find the scalar product of the following pairs of vectors and the angle between them. `hati-hatj` and `hatj+hatk`

Explanation

Let `veca = hati-hatj, vecb = hatj+hatk`
Then `|veca| = sqrt2, |vecb| = sqrt2`
Now `veca.vecb = 1xx0-1xx1+0xx1 = 0-1+0 = -1`
if `theta` is the angle between `veca` and `vecb` then
`theta = cos^(-1) ((veca.vecb)/(|veca||vecb|))`
=`cos^(-1)(-(1)/(sqrt2 sqrt2)) = cos^(-1) (-1/2) = (2pi)/3`.