added math macros for argmin and argmax

cel-thesis.cls

@@ -90,6 +90,11 @@
         #1\\[-1ex]#2%
     \end{array}\hspace*{-1ex}\Big)\,%
 }
+
+%% Define always missing math symbols. 
+\DeclareMathOperator*{\argmin}{\arg\!\min}
+\DeclareMathOperator*{\argmax}{\arg\!\max}
+
 % Graphics %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 % Ueberschriften fett
 \setkomafont{sectioning}{\normalcolor\bfseries}