# Euler-Lagrange equations

Lapidus
In this document, how do I get 3.2 on page 12? I assume it is the Euler-Lagrange equation given in 3.1 just rewritten. But how?

$$\frac{d}{dt} \frac{\partial L(q,\dot{q})}{\partial \dot{q}^{i}} =\frac{\partial^2 L}{\partial \dot{q}^{i} \partial q^{j}} \frac{dq^{j}}{dt} + ...$$