\[\begin{array}{l}
 T6. \to \int {\sin xdx}  =  - \cos x + C \\ 
 {\rm{Dokaz}}\,{\rm{(Proof):}} \\ 
 \int {\sin xdx}  = \left| \begin{array}{l}
 \cos x = t \\ 
  - \sin xdx = dt \\ 
 \sin xdx =  - dt \\ 
 \end{array} \right| =  - \int {dt}  =  - t =  - \cos x \\ 
 \end{array}\]