If `vec(a) = hat(i) + 2hat(j) - 3hat(k)` and `vec(b) = 3hat(i) - hat(j) + 2hat(k)` find the angle between the vectors `2vec(a) + vec(b)` and `vec(a) + 2vec(b)`.

Answer

`cos^(-1)((31)/(50))`