Answer:
a) 
b) 
c) the points of the form (x, -x) for x≠0
Step-by-step explanation:
a)
If φ(x, y) = arctan (y/x), the vector field F = ∇φ would be
On one hand we have,
On the other hand,
So
b)
The domain of definition of F is
i.e., all the plane X-Y except the (0,0)
c)
Here we want to find all the points such that
where k is a real number other than 0.
But this means
So, all the points in the line y = -x except (0,0) are parallel to the vector field F, that is, the points (x, -x) with x≠ 0
Given:
The function is:

To find:
The value of
.
Solution:
We have,

Putting
, we get



On combining like terms, we get


Therefore, the required function is
.
The answer should be $31.80.
Hope this helped!!!:)
$417.50 should be the correct answer you just multiply the $7.25 to 30 and then add the $200.