burgerandcheese
Junior Member
- Joined
- Jul 2, 2018
- Messages
- 85
They are applying the product rule to \(\displaystyle \dfrac{d}{dx}\left(u \times \dfrac 1 \nu\right)\)
\(\displaystyle \dfrac{d}{dx}\left(u \times \dfrac 1 \nu\right) = \dfrac{du}{dx}\times \dfrac 1 \nu + u \times \dfrac{d}{dx}\left(\dfrac 1 \nu\right) \)
\(\displaystyle \dfrac{d}{dx}\left(\dfrac 1 \nu\right) = \dfrac{d}{d\nu}\left(\dfrac 1 \nu\right)\dfrac{d\nu}{dx} =
\left(-\dfrac{1}{\nu^2}\right) \dfrac{d\nu}{dx}\)