TeX Quellcode:
\begin{array}{rclll}\dfrac{dt}{ds} &=& \cos(s) \cr ds &=& \dfrac{dt}{\cos(s)} \cr\cr\cr \displaystyle\int \dfrac{\cos(s)}{\sin(s)}\,ds &=& \displaystyle\int \dfrac{\cos(s)}{t}\cdot \dfrac{dt}{\cos(s)} \cr\cr &=& \displaystyle\int \dfrac{1}{t}\,dt\cr\cr &=& \ln\vert t\vert+c \end{array}