# Deriving equation from 3D Euler Equations.

## Homework Statement

I've got the 3D Euler equations
$\frac{\delta u}{\delta t} + (u\cdot \nabla)u = -\nabla p$
$\nabla \cdot u = 0$

I've been given that the impulse is
$\gamma = u + \nabla\phi$

## Homework Equations

And I need to derive
$\frac{D\gamma}{Dt} = -(\nabla u)^T \gamma + \nabla \lambda$
$\frac{D\phi}{Dt} = p - \frac{\left|u\right|^2}{2} + \lambda$

## The Attempt at a Solution

I've subbed the impulse equation into the first equation but don't really know where to go from there?