By using the properties of parallel lines, it can be inferred that -
Corrosponding angle goes in the place of first question mark and substitution property of equality goes in the place of second question mark.
What are parallel lines?
Two lines are said to be parallel if on extending them indefinitely, they will never intersect
Transversal is a line that intersects two or more parallel lines
For the first question mark
[Corrosponding angle]
For the second question mark
[Substitution property of equality]
To learn more about parallel lines, refer to the link-
#SPJ1
If there is such a scalar function <em>f</em>, then
Integrate both sides of the first equation with respect to <em>x</em> :
Differentiate both sides with respect to <em>y</em> :
Integrate both sides with respect to <em>y</em> :
Plug this into the equation above with <em>f</em> , then differentiate both sides with respect to <em>z</em> :
Integrate both sides with respect to <em>z</em> :
So we end up with