% ***** Custom symbols **************
% ***********************************
% Change del operator to d (for maxima)
% http://tex.stackexchange.com/questions/178946/better-automatic-spacing-of-differential-d
\renewcommand{\d}[1]{\mathop{\mathrm{d}{#1}}\!{}}
\newcommand{\del}[1]{\d{\left(#1\right)}}
\newcommand{\diff}[2]{
  \frac{\d{}}{\d{#2}}
  \left(#1\right)}
\newcommand{\deriv}[2]{
  \frac{\del{#1}}{\d{#2}}}