9.9.1 Potential and solenoidal fields
(3)
Problem:
Show that the vector field \( \vec{a} \) is potential and find its potential:
\[
\begin{array}{l}
\vec{a}=y z \cos x y \cdot \vec{\imath}+z x \cos x y \cdot \vec{\jmath}+\sin x y \cdot \vec{k}, \\
M_{1}(1,1,1), \quad M_{2}(0,0,0)
\end{array}
\]