TeX Quellcode:
\begin{array}{rcll}r\left(\sqrt{2}\right) &=& \sqrt{\dfrac{\left(\sqrt{2}\right)^4}{2}}-\sqrt{2} \\&=& \sqrt{\dfrac{4}{2}}-\sqrt{2} \\&=& \sqrt{2}-\sqrt{2} \\&=& 0 \end{array}