Problem:
Find the angle between the following two vectors:
$\left(
\begin{array}{c}
 0 \\
 2 \\
 -1 \\
 -8 \\
\end{array}
\right)$ and
$\left(
\begin{array}{c}
 4 \\
 -3 \\
 -3 \\
 2 \\
\end{array}
\right)$.
Answer:
$\cos ^{-1}\left(-\sqrt{\frac{19}{138}}\right)$
{'source': 'AMPS', 'file': 'amps/mathematica/linear_algebra/vector_angles_and_projections/22467.txt'}