I am trying to get this to display:
My current attempt is :
\begin{equation}
\begin{align}
\frac{\dd{x_c^{*}(t,u)}}{\dd{u}}=\gamma + \alpha \lambda \{[r(t)-x(t,0)]\\
+ \frac{1}{1+\alpha\beta\lambda}[\frac{\dd{r(t)}}{\dd{t}}-\gamma]
\end{align}
\end{equation}
I have defined a macro \dd
above as (uses the physics
package) :
\newcommand{\dd}[1]{\mathrm{d}#1}
I couldn't find how to display that vertical line next to the derivative ( just left of the = sign ) with u=0
on it. Everything else displays fine with my code.