1 : you would use a graduated cylinder . 2 : , you would use a yard stick or maybe a ruler if you are not able to find one. You can also use a meter stick.

is conservative if there is a scalar function
such that
. This would require



(or perhaps the last partial derivative should be 4 to match up with the integral?)
From these equations we find





so
is indeed conservative, and the gradient theorem (a.k.a. fundamental theorem of calculus for line integrals) applies. The value of the line integral depends only the endpoints:


K is whatever you want it to be