Problem:
Find the angle between the following two vectors:
$\left(
\begin{array}{c}
 -6 \\
 9 \\
 3 \\
 3 \\
 -6 \\
 5 \\
\end{array}
\right)$ and
$\left(
\begin{array}{c}
 0 \\
 2 \\
 2 \\
 1 \\
 8 \\
 -10 \\
\end{array}
\right)$.
Answer:
$\cos ^{-1}\left(-\frac{71}{14 \sqrt{173}}\right)$
{'source': 'AMPS', 'file': 'amps/mathematica/linear_algebra/vector_angles_and_projections/24536.txt'}