\[\begin{array}{l}
 T13. \to \int {\cosh xdx}  = \sinh x + C \\ 
 {\rm{Dokaz}}\,{\rm{(Proof):}} \\ 
 \int {\cosh xdx}  = \left| \begin{array}{l}
 \sinh x = t \\ 
 \cosh xdx = dt \\ 
 \end{array} \right| = \int {dt}  = t = \sinh x \\ 
 \end{array}\]