Answer
$\theta=\arccos(\frac{7}{30})$
Work Step by Step
We are given: $u=(-2,-1,2,4)\\
v=(-3,5,1,1)$ in $R^4$
Let $\theta$ be the angle between $u$ and $v$.
We obtain:
$$\cos \theta=\frac{}{||u||.||v||}\\
=\frac{(-2).(-3)+5.(-1)+2.1+4.1}{\sqrt (-2)^2+(-1)^2+2^2+4^2.\sqrt (-3)^2+5^2+1^2+1^2}\\
=\frac{7}{\sqrt 30}$$
$$\rightarrow \theta=\arccos(\frac{7}{30})$$
