Line integral over a small length
Solution 1:
Mean value theorem for integration
$$\int_a^{a+h} f(x) \, dx=hf(\xi)$$
for some $\xi \in (a,a+h)$.
Line integral over a small length
Solution 1:
Mean value theorem for integration
$$\int_a^{a+h} f(x) \, dx=hf(\xi)$$
for some $\xi \in (a,a+h)$.